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FIRST STEPS 



m 



ELECTEICITY 



DESIGNED FOR THE ENTERTAINMENT 

AND INSTRUCTION OF YOUNG PEOPLE AT HOME 

AND IN SCHOOL. 



BY 



CHARLES BARNARD 






20 I88& 

NEW YORK: 
CHARLES E. MERRILL & CO. 

1888 



PUBLISHERS' NOTICE. 

For the convenience of those who cannot readily 
obtain the different pieces of apparatus mentioned in 
this book, the publishers have prepared an Electrical 
Outfit comprising most of the articles used in perform- 
ing the experiments described, which they will send by 
mail, securely boxed and postpaid, for $1.50. A cir- 
cular, descriptive of this outfit, will be sent free on 
application. The more elaborate and expensive ap- 
paratus may be obtained from any of the dealers in 
electrical goods. 



A 



COPYRIGHT, 1887 

By CHARLES E. MERRILL & CO. 



PEEFATOEY NOTE. 



The aim of this book is to describe a number of 
simple and inexpensive experiments in electricity that 
can be performed in schools, the lecture-room, and 
the home circle. Xone of the experiments are at all 
difficult or dangerous, nor are the materials, if used 
with ordinary care, likely to do the slightest harm to 
furniture or clothing. The aim is also to enable the 
reader to obtain a general idea of the laws governing 
the manifestations of this force in nature, and to see 
how this force is used in the arts, in business, and in 
manufactures. It is the hope of the author that the 
book may be of use as a school reader, as a guide to 
home amusements in science for winter evenings, and 
as a help to all who wish to get a notion of the general 
principles underlying the great modern inventions in 
electricity. Charles Barnard. 

New Eochelle, X. Y., Jan., 1888. 



CONTENTS. 



Chapter I. The First Steps. Asking Questions of 
Nature. Attraction. Conduction. Grey's 
Experiment 5-19 

" II. Frictional Electricity. Conductors. Non- 
conductors. The Electroscope. Du Fay's 
Experiment. Insulators. The Dancing 
Feather. Like Repels — Unlike Attracts, 20-39 

" III. Induction. Franklin's Idea. The Egg Ex- 
periment. The Electrophorus. The Ley- 
den-Jar 40-59 

" IV. Static Electricity. Points and Knobs. 
The Continuous Induction Machine. 
Franklin's Experiment . f . . 60-74 

" V. Magnetism. Magnets. Magnetic Induction, 75-84 

" VI. Current Electricity. The Battery. The 
Needle in a Current. The Galvanometer. 
The Electro-Magnet .... 85-99 

" VII. The Last Steps. The Induction Coil. 
Electricity from Magnetism. Magneto- 
Electricity. Electric Bells. The Electro- 
Magnet at Work. The Telegraph. The 
Telephone. The Dynamo. Electric Motors. 
The Storage Battery. The First Telegram. 
The Unity of Nature . . . 100-133 



FIRST STEPS IN ELECTRICITY. 



CHAPTER I. 



ASKING QUESTIONS OF NATURE. FRICTION AND ELEC- 
TRICITY. ATTRACTION AND CONDUCTION. 

The afternoon is warm and sultry. There are daz- 
zling mountainous clouds built high in the blue sky. 
In the west the billowy masses seem duller and take on 
tints of pale red in the hazy air. There is a movement 
among these sierras in the west, and they mount 
higher and shut out the sun. There are darker shad- 
ows below. A vast arch of greenish gray clouds, 
ragged and torn, creeps up the sky, and behind it is an 
ashen veil of rain. From the threatening clouds leap 
flashes of light. Suddenly there seems a more vivid 
flash and a tall tree is split open and falls to the 
ground, while terrible peals of crashing thunder fill the 
air and drown the roar of the wind and the shrill so- 
prano of the rain sweeping through the woods or 



6 FIRST STEPS IN ELECTRICITY. 

whitening the water in the river. After the shower 
has passed we go out and inspect the fallen tree. It is 
shattered* and torn as if struck some terrible blow. 

A young girl combing her long hair in a cold room 
on a frosty morning hears soft crackling sounds in her 
hair as her comb slips through her tresses. 

A woman going out for a walk on a cold day sees 
some lint on her dress and tries to brush or pull it off 
and finds that, for some reason, it clings to the fabric. 
A bit of feather floating near her dress seems to be be- 
witched and flies through the air and sticks to it as if 
it were warm wax. 

Some children playing with a cat in a dusky room 
on a winter's night see tiny flashes of light in the cat's 
fur. Every stroke of affection they bestow on the 
cat's back is rewarded with a touch of fire. 

Here are four curious things you have, perhaps, 
seen many times. We say they are natural phenomena. 
What do they mean, are they in any way related to each 
other ? Why did they appear ? Now there are three 
steps you can take. You can ask some one about 
them, you can find a book that will tell you some 
facts concerning them, or you can examine the 
phenomena for yourself and find out by asking ques- 
tions of nature. It is a good idea to ask people to ex- 



ASKING QUESTIONS OF NATURE. 7 

plain things and it is not difficult to sit in a comfort- 
able chair and read a book. It is far pleasanter and 
every way better to find out for yourself. 

All things — plants, animals and inanimate objects, 
planets, stars, grains of dust in the road and star-dust 
in the sky — behave in a certain way under certain cir- 
cumstances. The behavior of anything is the result of 
some law, and this behavior shows what the law is. A 
heavy book in the hand, if let fall, drops upon the 
ground. It behaves in that particular manner because 
there is a law that it should fall unless supported. 
The law of gravity caused the book to behave in that 
way, and its behavior is evidence of the law. Try 
this again. Try it many times, and the result is the 
same. We are compelled to think there is a law 
governing the book's fall. 

Take a light feather out of doors in the wind, and let 
it fall. It floats away, perhaps out of sight, without fall- 
ing. Here seems to be an exception to the law. Get an- 
other feather and try it again in a closed room. It flut- 
ters to the floor. There is no exception and we conclude 
that the feather floating away on the wind behaved in 
that manner because controlled by some other law that, 
for the time, was stronger than the law of gravitation. 

We have performed an experiment. By means of 
the book and the feathers we asked questions of nature. 



8 FIRST STEPS IN ELECTRICITY. 

We placed them under certain circumstances, and by 
watching their behavior, learned something of the laws 
governing them. We cannot call this hard work, for 
the experiment was interesting and it was only a 
pleasure to make it. The search for knowledge of the 
world by means of experiment is one of the greatest 
pleasures you can have, and you will find that this 
method of getting at facts in nature is quite as useful as 
asking questions of people or reading good books. All 
that is known of nature and her laws was found out by 
experiment, by studying the behavior of common 
things. 

Suppose the children, wishing to see the curious 
sparks on the cat's back at another time, had taken 
her into a warm, well lighted kitchen, or out of doors on 
a summer day and then repeated the experiment. They 
would be disappointed. Not a spark would appear. 
They would really be repeating the experiment under 
different circumstances and the result would not be 
the same. They might imagine that the sparks were 
made by the cat, but would at once wonder if she did 
it, why she could not be good enough to let off her 
little fire- works at one time as well as another. If 
they were wise children they would not make this mis- 
take, and would conclude that the experiment had 
been performed under different circumstances and that 



ASKING QUESTIONS OF NATURE. 9 

therefore the sparks behaved in a different way and 
refused to appear. Plainly, the children would really 
begin to learn something about this matter. They 
would see that the phenomenon appeared only in a cold 
dark room and not in a warm light one. It is evident 
that this method of hunting for facts with a common 
thing like a cat is a very pleasant way of studying 
nature. The children did not rind much, yet it was 
really something, for they proved that light and heat 
in some way affected the sparks observed in the cat's 
fur. They also proved, incidentally, that the cat her- 
self had no hand in this sparking business. 

You can study these four phenomena and many 
others equally curious by simply experimenting or ask- 
ing questions of nature. It is our plan to now do this 
by actually performing experiments and by a little 
reading to try and understand what the experiments 
mean. All you need is a willingness to learn and pa- 
tience. Do not be afraid to try many times over. Do 
everything slowly and thoroughly. Eemember always 
that while nature is dumb, she never makes mistakes. 
Keep full and complete notes of all you do. Have a 
pad and stylographic pen handy at all times and record 
everything you do or see at the time the experiment is 
made. Shall we now go on ? 

For the experiments we are to perform, we need first 



10 FIRST STEPS IN ELECTRICITY. 

a suitable time and place, and secondly certain simple 
tools and apparatus. For all the experiments the best 
time is the evening and in winter. Cold dry weather 
is better than warm or damp weather. If the experi- 
ments are performed in the daytime choose a sunny 
day in preference to a cloudy day. The best place is a 
warm, dry room where there is an open fire. In the 
daytime select a room with sunny windows. In all 
the first experiments there must be some means of 
warming our apparatus, either by placing them before 
a fire or in the sunshine. 

The best table for our work is a common wooden one, 
and for a cover use brown wrapping paper or place on 
the table a pine board, smooth and dry. On this board 
or on the wrapping paper, place all the apparatus used 
in the experiments. Take particular pains to see that 
the board and the paper are dry, and to make sure 
hold them to the fire just before you begin your work. 

Next we shall need about a quarter of a yard of good 
silk — any remnant of dress goods will answer. Cut 
this into pieces six inches square; and placing one over 
the other stich them together to form a pad or holder. 
Pull out or unravel from the silk or from a ribbon or 
any fabric a few light pieces of yarn or ravellings. 

Get also a small piece of loose cotton batting. 
From the dealer in painters' materials get a leaf 



ASKING QUESTIONS OF NATURE. H 

or two of a thin foil (like gold leaf) made of an alloy 
called Dutch metal. If a leaf cannot be procured, buy 
a whole " book w which is the name given to a little 
package of the foil. Next, w r e need a glass tube of 
some kind. The chimney of a student lamp will 
answer : a rod or stout tube about half an inch in 
diameter and eighteen inches long is much better and 
and is very cheap. Pull from the cotton batting a 
couple of little tufts and cut from the Dutch metal 
foil several pieces half an inch square. See that the 
glass and the silk are clean, and then, having warmed 
all these materials before the fire, place them on a dry 
board on the table. 

Nothing whatever happens. None of the things 
seem to have the slightest influence upon each other. 
Putting these things close to each other does not pro- 
duce any change or effect of any kind. Now take the 
tube and pad to the fire and make them quite hot. 
Then hold the tube in the right hand, and wrapping 
the pad about it, with the left rub the pad briskly 
along the tube for a moment or two. Now, on holding 
the tube over the things on the board, they behave in 
the most singular manner. They leap up to meet it 
and even cling closely to the glass. Take them off and 
repeat the experiment and they appear more animated 
than ever. Repeat the experiment in another way. 



12 FIRST STEPS IN ELECTRICITY. 

Let one person hold a tuft of cotton in the hand over 
the head and then drop it. As it floats on the air, let 
another bring the rubbed tube near it. The cotton 
behaves in the most surprising manner, leaping 
through the air to reach the tube. 

Eepeat the experiments several times, observing care- 
fully everything that happens. Best a moment and 
draw the tube through the hand. Xow lay it upon the 
foil and threads, and nothing happens. Whatever the 
cause of the singular behavior of these things during 
our experiments it has now ceased to work and they 
are no longer drawn to the glass. The effects we 
observed have completely disappeared. Eub the glass 
again with the pad, and they all reappear. 

We observe that the glass attracts the threads and 
foil only after it has been rubbed with silk, and that 
the attraction is but temporary. The rubbing with 
silk plainly excites this property in the glass, and for 
convenience, we will say the glass is excited after it 
has been rubbed by the silk. Excite the glass and try 
it on other light materials, paper, smoke, an empty 
egg shell, or on the hair of the head, and make a list 
of all the things you can procure which are attracted 
by the glass. 

Procure a tumbler of the best quality of glass to be 
found, wipe it dry and place it upside down on the 



ASKING QUESTIONS OF NATURE. 



13 



board. Pull a bunch of fine threads (the filling) from 
a ribbon, twist them together at one end, and place 
the bunch on top of the tumbler with the loose ends 
hanging over the side, and lay a cent or other coin on it 
to keep it in place. Excite the glass and hold it before 
the threads, taking care to hold the part which has 




No. I. 



been rubbed opposite the threads. Instantly they will 
rise and stretch out towards the glass, every little fila- 
ment standing apart from the others. 

Picture No. I. shows how the threads behave when 
the glass is brought near them. Move the glass about, 
and the threads follow it as if alive. Brush the glass 
with the hand and repeat the experiment twice. 



14 FIRST STEPS IN ELECTKICITY. 

We have performed experiments which have been 
repeated many times for centuries. Long before the 
Christian era began men observed with wonder that 
if a substance called electron, and which we now know 
is yellow amber, be rubbed, that it has this power of 
attracting light bodies held near it. For centuries 
this could not be explained, nor can it be fully ex- 
plained even now. We know nothing more than this : 
the behavior of these things is due to a certain force in 
nature which has received the name of electricity. It 
is easy to see where the name came from when we re- 
member that these experiments were first performed 
with yellow amber or electron. 

It is very difficult to say precisely what electricity is, 
and for the present we must leave the matter in sus- 
pense and wait till further experiments tell us more 
about it. For convenience we will say that these curi- 
ous effects are produced by electricity and that we can 
produce these electrical effects by rubbing or friction. 
Already you see we have learned something from our 
experiments. You have discovered that when glass is 
rubbed with silk the glass is excited to electrical action, 
and when thus excited or electrified it will produce 
some very singular effects. 

One more experiment. Procure an egg and an egg 
glass or small wineglass and set the egg upright in the 



ATTRACTION. 



15 



glass. Then get a slender pine stick about a foot 
long. A yard-stick can be used, if the pine stick is 
not handy. Carefully balance the stick on top of the 
as in Picture No. II. 
Excite the glass and hold it beside the end of the 




No. II. 

balanced stick, and at once it swings round towards 
the glass. With a little practice it can be made to 
follow the glass round and round, clearly showing the 
stick is attracted by the excited glass. 

You have now two facts — electricity can be excited 
by friction and this electricity has the power of at-- 



16 FIRST STEPS IN ELECTRICITY. 

traction. By doing several experiments you plainly 
show that there is a law in the matter. Whatever 
behaves in a certain way every time it is placed in 
the same conditions we say is subject to a law. In 
this case we discover there is a law that electricity 
attracts. You have demonstrated the existence of 
electrical attraction, and as it repeats itself every time, 
we say there is a law of electrical attraction. 

Having made one step in our work of discovery you 
can now use the knowledge thus gained to get still more 
knowledge. Let us use this knowledge to perform 
other experiments and see what new facts we can 
learn in regard to the behavior of things under the 
influence of electricity. 

Rub the glass again and hold it over the tufts of 
ravellings on the tumbler, but quite high, say a yard 
or more over them. K"o effect. They do not appear to 
be affected while the glass is at that distance. Rub it 
and bring it slowly nearer the table, stopping at inter- 
vals to see when the attraction begins. It is plain 
that the electrical attraction does not extend very far 
from the glass. Try to be exact and make a note of 
the distance at which the attraction appears to begin. 

Now let us try another experiment, using a part of 
the information you just gained. Get a piece of fine 
copper wire somewhat longer than the distance at which 



CONDUCTION. , 17 

you found the things began to be attracted. For in- 
stance, if the things began to fly up to the glass when 
it was six inches above them, make the wire not less 
than ten inches long. The best plan is to exceed the 
limit and the wire should be about eighteen inches 



No. III. 

long. Get a copper two-cent piece and suspend it 
from one end of the wire by twisting the wire round 
the coin. Then twist the other end of the wire round 
the end of the glass tube as shown in Picture 
No. III. 

Carefully holding the tube in the hand rub it with 
the silk pad close up to the wire while the copper 
2 



18 FIRST STEPS IN ELECTRICITY 

coin is hanging by the wire in the air. Then hold the 
tube oyer the tumbler so that the cent on the end of 
the wire will be over the little bunch of ravellings. At 
once the threads are attracted towards the metal pre- 
cisely as in our other experiments it was attracted to 
the glass. The tube is too far away to influence the 
threads, and we are obliged to think that in some 
strange fashion this power of attraction travelled down 
the wire to the coin and affected the ravellings, causing 
them to fly up precisely as in one of our other experi- 
ments. This is clearly shown in Picture No. III. 

Kepeat this experiment with other things and you 
will plainly see that all the effects of attraction take 
place near the coin on the end of the wire precisely as 
when you used the glass rod alone. Who first dis- 
covered by experiment that electron had this power of 
attraction is not known. It was observed by a number 
of people a long time ago, and yet not one of them 
seems to have tried to learn more or to have taken the 
little step in advance that you have just taken. It was 
not till quite modern times that it was learned that 
this power of attraction could be made to travel over 
a wire. Even then it was learned only by experiment. 
When in 1729 Stephen Grey discovered this curious 
property of electricity it was probably not known, and 
certainly was not mentioned in any book. He could 



GREY'S EXPERIMENT. 19 

not, as people can now, read about it, and only by this 
very experiment you have just performed was he en- 
abled to make this remarkable discovery. If it had 
not been known before, you, too, might have made 
yourself famous by its discovery. Stephen Grey 
fastened a long linen thread to a glass rod and hung 
it out the second story window of his house, and 
discovered that when the tube was rubbed the coin 
on the end of the thread attracted light substances on 
the ground below. 

A good way to repeat the experiment is to fasten a 
long fine wire to the glass tube and hang it in the well 
of a staircase. Let one person hold and rub the tube, 
and let another go down-stairs and place the ravellings 
near the copper coin. Take pains that the wire is sus- 
pended clear of the stairs and that the experiment is 
done on a dry day when the glass and silk pad are warm 
and dry. This property which the copper wire and 
cent show is called conduction. We say electricity can 
be conducted and we call the wire a conductor. 



CHAPTER II. 

THE ELECTROSCOPE. CONDUCTORS AND INSULATORS. 
DU FAY'S EXPERIMENT. THE DANCING FEATHER. 
ATTRACTION AND REPULSION. 

The experiments you have performed have shown us 
three things concerning electricity. First it can be 
excited by friction or rubbing, as when you rubbed the 
glass tube with the silk pad. Friction caused it to 
appear and when it appeared we learned that it had the 
power of attracting light bodies. It attracts every- 
thing, but only the small, light materials we used 
showed it plainly enough for us to see and notice it. 
It can be conducted through copper, and copper is a 
conductor of electricity. Observe we have neither seen, 
heard, nor felt the electricity. We have seen only how 
it affects certain things and how it behaves when given 
a conductor. While we could not see it travel down the 
copper wire, we are very sure it did, because it pro- 
duced the same effects at one end of the wire as at the 
other, though the w T ire might be many yards long. In 
other words your experiments have shown us the laws 
of electrical attraction and electrical conduction. Not 

20 



THE ELECTROSCOPE. 21 

fully, because there may be much more to learn con- 
cerning these laws, but enough to prove that there are 
such laws. 

AVe also noticed one other thing. When, after 
any experiment had been performed, the tube was 
drawn through the hand it lost all power of attraction. 
We must conclude from this that the power of attrac- 
tion was not in the glass, because, if it were, why does 
not the glass always attract ? When the glass is rubbed 
we say it is excited to electrical action or, in other 
words, is charged with electricity. When we draw the 
tube through the hand all the electrical effects disap- 
pear, and the inference is that the electricity has in 
some manner left the glass and disappeared. We, 
therefore, say it is discharged. What really happens 
when the tube is discharged in this way is that the 
hand becomes a conductor and carries the electricity 
off and it is practically lost — that is, lost as far as our 
experiments are concerned. To get new effects we 
must charge the glass over again by means of more 
friction. 

We now need a more convenient method of finding 
out when anything is charged or discharged and you 
must construct a more complicated apparatus than any 
we have used before. 

Procure a fruit-jar or wide-mouthed bottle and wipe 



22 



FIRST STEPS IIS; ELECTRICITY. 



it clean and dry. Fit a wooden cork to it or place a thin 
slip of wood on the mouth. Get a short piece of stout 
copper wire, and bend about one inch of one end at a 
right angle. Pass it through the wood so that the bent 
end will hang in the bottle as in Picture No. IV. Eoll 




No. IV. 

up the other end of the wire into a little knob or ball. 
Next cut a strip about an inch wide and three inches 
long from a leaf of the Dutch metal foil we used before, 
and hang this strip on the bent end of the wire in the 
jar as shown in Picture No. IV. 

This apparatus is called an electroscope, and we shall 



THE ELECTROSCOPE. 23 

use it in a number of experiments to show the presence 
of electricity. Eub the tube and hold it aver the little 
knob at the top of the wire, as shown in the picture. 
At once you will observe a curious effect in the little 
strip of foil suspended in the jar. The two parts or 
leaves fly apart. Touch the knob with the finger 
and they fall together again. We bring the charged 
tube near the copper wire (conductor) and the leaves 
fly apart. They are charged with electricity. We 
touch the wire and discharge it and they fall down 
again. Why they do this we will not stop to discover. 
It will be plainly shown by later experiments. Just 
now we will only notice that an electroscope is an ap- 
paratus for showing the presence of electricity, and by 
its aid we can go on to other experiments. 

Make another pad as before, using, instead of silk, 
common flannel. Then get a stick of sealing-wax, the 
larger the better, and rub it with the flannel as we 
rubbed the glass tube with the silk. On holding the 
sealing wax over the bits of cotton and foil, we find the 
charged wax has precisely the same properties as the 
excited tube. We conclude from this that friction 
between other materials beside silk and glass can excite 
electrical action and give electrical effects. 

You will find it a good plan to repeat all your experi- 
ments with the charged sealing wax, because while you 



24 FIRST STEPS IN ELECTRICITY. 

get the same results they are not so strong or marked 
as with the glass tube. From this we find that there 
may be a difference in the amount of attraction or other 
effects, though in kind they are alike. Try the wax 
also with the electroscope. 

Having observed that electricity can be obtained 
from glass and sealing wax, we might go on and 
find that by friction electricity can be developed from 
many things. Warm a writing pad of Manilla paper 
before the fire, and rub the top sheet briskly with the 
hand, and it will be found that this sheet will be 
strongly attracted to the one beneath it. Many other 
things will display the property, and it is highly prob- 
able that all friction excites electricity in a greater or 
less degree. Electricity obtained by friction for this 
reason is called frictional electricity. 

It is said that some one once brought to Faraday * a 

*" Faraday," Michael. (1791-1867). An English chemist, 
and philosopher. He presents a remarkable instance of the 
success to be gained over such obstacles as poverty and lack of 
education, by patience and perseverance. At the age of thir- 
teen he was apprenticed to a book-binder, but employed all of 
his spare moments in studying science, and in making experi- 
ments with implements of his own manufacture. He attended 
several evening lectures on chemistry, given by Sir Humphrey 
Davy, and ventured to send to the lecturer himself the notes 
he prepared on the lectures, which resulted in gaining for him 



THE ELECTROSCOPE. 25 

new experiment with a request that he would examine 
the results to be obtained. " Stop a moment," said 
Faraday, "before you begin, tell me what I am to ob- 
serve." So we must learn what to observe. So far we 
have observed only the attraction caused by the rubbed 
glass or wax. Eepeat the experiment with the glass 
tube, silk pad, and bits of foil. The bits of metal leap 
up to the glass, and then some of them fall back again, 
and again leap up, perhaps repeating the little flights 
up and down several times. Here is plainly something 
else to be observed. Why should the bits of foil be- 
have in that manner? Are they attracted and then 
repelled? Is the attraction suspended for a few sec- 
onds, and then resumed? Clearly there is here a 
wholly different behavior, and we must infer there is 
another law governing it. We must find out this law 
by other experiments. We have already learned that 
electricity can be conducted through copper. Can it 
be conducted through other things? You must find 

the position of assistant in the Eoyal Institution. Later, he 
accompanied Davy, as amanuensis, on a tour over the conti- 
nent which lasted a year and a half. Shortly after this he 
began lecturing, and publishing articles on scientific subjects, 
and then there began that long series of important discoveries, 
accounts of which he gave to the public in volumes, having 
the subjects arranged according to their position in science. 



26 FIEST STEPS IN ELECTRICITY. 

an answer to this question before you can solve the 
others. 

Get the glass, silk pad, the fine copper wire and the 
electroscope. Twist one end of the wire round the end 
of the glass tube as before, and twist the other end round 
the copper rod of the electroscope. Kub the tube with 
the silk, and instantly the two leaves of the electroscope 
start up, rising and falling slightly at every stroke of 
the rubber. Clearly the electricity developed by fric- 
tion is conveyed through the copper wire. 

We may make this experiment on a large scale by 
dropping a wire down the well of the stairs, and causing 
the leaves of the electroscope to be expanded on the 'first 
floor by rubbing the glass on the fourth floor. 

Next procure about a yard of sewing silk. Tie one 
end of it to the end of the glass tube (without the wire), 
and the other end to the copper wire of the electro- 
scope. You may rub the tube as hard as you please 
and there is no effect in the electroscope. To prevent 
any mistakes in the matter, use the sealing wax and 
flannel pad with the silk thread in the same way and 
the result is still the same. Your experiments prove 
that there is a difference between the copper wire and 
the sewing silk. As the little leaves are quiet while 
the glass or wax is rubbed, though connected by the 
thread, the inference is that the electricity cannot 



XOX-COXDUCTORS. 



27 



travel through silk as it does through copper. We 
conclude then that some things do not conduct elec- 
tricity, and we may call such things non-conductors. 
Thus with the glass rod and the electroscope you can 
now make a series of tests with different materials and 




No. Y. 

find out which are conductors and which are non- 
conductors. Try brass and iron wire, cotton twine, 
linen thread or any other material. Arrange each ex- 
periment as in Picture No. V. 

Observe each trial carefully and make a list of all 
the things used, whether they are conductors or non- 
conductors. We shall return to this matter presently 



28 FIEST STEPS IN ELECTRICITY. 

and make further experiments with other apparatus. 
Meanwhile, fasten the silk thread (taking pains to see 
that it is perfectly dry) to the glass and the electro- 
scope as in Picture No. V., and you can repeat Du 
Fay's * celebrated experiment in conduction. While the 
thread is dry no electricity is conveyed by the silk. 
Now carefully wet it through its whole length. Now 
the leaves of the electroscope fly apart at every stroke 
on the glass. Has the silk become a conductor? No. 
It is the water on the silk. Thus we see that water is 
a conductor, and that any non-conductor may become a 
conductor when wet with water. Kepeat the experi- 
ment with other non-conductors, both dry and wet. 

As it is not easy to try anything but threads and 
wires in this way, you may continue the experiment in 
another form. 

Take a small sheet of tissue paper, and, folding it 
into a long and narrow strip, cut up one end into rib- 
bons to form a tassel. Bend a hairpin in the middle to 
form a hook, push it through the tassel and suspend it 
by a silk thread from a gas lamp (or other projecting 
piece of furniture), as in Picture No. VI. 

We are about to make an experiment that will teach 

* "Du Fay," Charles Francois. (1698-1739). A French scholar 
who made many researches concerning the barometer, the mag- 
net, electricity, etc. 



DU FAY'S EXPERIMENT. 



29 



us several things concerning the behavior of objects 
under the influence of electricity; but just now we will 
follow Faraday's example, and ask which of the various 




No. VI. 
phenomena we are to observe. We wish to examine a 

number of things to see which are conductors, and 

which non-conductors. We will observe this only at 



30 FIRST STEPS IN ELECTRICITY. 

present, and examine the other points a little later. 

Bub the glass tube, and touch it. to the ends of the 
hairpin. At once the paper tassel starts out in every 
direction. We may even take the tube away and the 
tassel will remain spread out. Touch it with the fin- 
ger, and it collapses, falls together, and hangs down 
with every ribbon straight. Do this several times. 
We charge the tassel with electricity, and then remove 
or discharge it with the finger, plainly showing that 
the hand is a conductor. Try discharging with glass, 
wood, wax, metals, and anything else you can find, and 
make a list of the conductors and non-conductors. 

Suspend the tassel by a copper wire, and repeat the 
experiment. ISTo effects can be obtained. The elec- 
tricity plainly leaks away through the wire. It seems 
the tassel must be suspended by silk — a non-conductor. 
Hang it up by the silk thread, and charge the tassel 
several times from the glass tube until the ribbons 
stand out in every direction. A little thought will show 
that, if *the silk is a non-conductor, we are storing elec- 
tricity in the tassel. If the air of the room is dry, the 
electricity cannot easily escape, and it remains in the 
tassel until it gradually escapes to the dust or invisible 
vapor in the air. 

You have now reached a point in which you begin to 
see the value of your experiments. They have shown 



IXSULATORS. 31 

you that electricity can be conveyed to a distance, as 
from the top to the bottom of a house, provided the 
wire does not touch anything. If you were to try it 
with a long wire placed horizontally, you must support 
the wire on something. If the supports are of metal, 
the electricity will pass through the supports and be 
lost. We may have already noticed in all this work 
that electricity is very fugitive or unstable. It escapes 
instantly at the first opportunity, seeking a way to 
the earth. To check this tendency to escape, you 
must support all conductors by non-conductors. 

So we find at the very outset of our studies a great 
law that must be observed in the practical use of electri- 
city. It can be conducted through the wire of a tele- 
graph or telephone or fire-alarm, but the wire must be 
suspended from non-conductors. Wood when wet, as 
in a rain storm, will conduct electricity, and yet the 
telegraph wire is on a wooden pole. This is true, but 
observe the glass knobs to which the wire is fastened. 
Glass, as was shown by the experiments made with the 
paper tassel in arranging your lists of conductors and 
non-conductors, is a non-conductor, and we call these 
knobs on the poles insulators because they insulate or 
cut off the escape of the electricity precisely as water 
may cut off an island from the main land. We know 
that telegraph lines are laid under the seas. If water 



32 FIKST STEPS IN ELECTEICITY. 

is a conductor how can that be ? Rubber, gutta-per- 
cha, silk, and other materials are wrapped round the 
wire to insulate the cable from the water. 

This knowledge of conduction and insulation, con- 
ductors and non-conductors, gained by experiment is, 
therefore, of the utmost importance in all work con- 
nected with electricity. To make it still more clear, 
connect a long wire with the glass and the electroscope, 
and lay it from room to room along the floor. So 
arranged the experiment may fail. Let the wire rest 
everywhere on glass tumblers placed on the floor and 
it will work. Glass, as you may recall by referring to 
your lists of conductors and non-conductors, is a 
non-conductor, therefore the tumblers are insulators. 

You can now return to the glass tube, the seal- 
ing wax, and the two pads and see what more can be 
done. You found that both glass and wax exhibit 
electrical attraction when charged by friction. Will 
electricity exhibit anything else ? Get a very small, 
light feather and fasten it to the end of a yard of fine 
sewing silk. Tie the other end of the silk to a 
bracket, hanging lamp, or other projecting piece of 
furniture and we will try a new kind of experiment. 
Picture No. VI. shows how the feather and silk are 
prepared for the work. 

Observe the condition of things. The feather is 



THE DANCING FEATHER. 33 

suspended by a non-conductor. It is insulated and 
will keep for a few moments any electricity given to it. 
Bring the excited glass near it. It flies to meet the 
glass, touches it, and at once darts away from it. Try 
your best to touch it again and the feather flies round 
and round, trying its best to keep away from the glass. 
It is plain that it is no longer attracted, but is re- 
pelled. It now exhibits repulsion as well as attraction. 

Discharge the feather by touching it and then 
recharge it, and at once hold one hand near the feather, 
and bring the rubbed glass near it and opposite the 
hand, or with the feather between the hand and the 
glass. At once a most extraordinary thing takes 
place. The feather leaps to the glass, and then flies 
to the hand, touches it, and then flies back again, only 
to repeat its little flight from glass to hand many 
times over. You remember the bits of foil be- 
haved in the same way, leaping up and down between 
the glass and board several times. If you have forgot- 
ten how it behaved, repeat the experiment. Here is a 
singular performance and yet, by the use of a little 
imagination, we can find out why the feather behaves 
in this peculiar way. 

Though we cannot see or hear or feel the electric- 
ity, we see its manifestations. The feather (when 
discharged) we may imagine as empty of electricity. 
3 



34 FIRST STEPS IN ELECTRICITY. 

We develop electricity by friction on the glass, and 
bringing the glass near the feather, find it is attracted 
to it, touches it for an instant, and then flies away. 
In that instant's touch, we can imagine the feather 
loaded (or charged) with electricity. It has taken 
some electricity from the glass and yet there is some 
left in the tube. This you can prove by discharging 
the feather (touching it) and recharging it from the 
glass without rubbing the glass again. Both are 
charged and now instead of attraction there is repul- 
sion. When we saw the feather, dart backward and 
forward between the glass and hand it was attracted 
and charged, then repelled. It flew to the hand, 
discharged itself and was ready to be reattracted and 
recharged, when it was at once repelled. We can also 
repeat the experiment with the sealing wax and see the 
feather behave in precisely the same manner. 

Now prepare for a much more complicated piece of 
work. Take the glass tube and let a friend take 
the sealing wax. Charge both by friction at the same 
time. When both are ready bring the glass near the 
feather. It is attracted, is charged, and then repelled. 
At once bring the excited wax near the feather and 
instead of being repelled it is attracted. Hold the 
glass on one side and the wax on the other, as in picture 
No. VII., and the feather will swing quickly from one 



THE DANCING FEATHER. 35 

to the other. Try it again slowly, noting that while 
the feather, when charged by the glass, is repelled, it 




No. VII. 



is attracted by the wax. On touching the wax it is 
repelled and is attracted by the glass, and thus, alter- 



36 FIKST STEPS IN ELECTRICITY. 

nately attracted and repelled, it flies from one to the 
other in a curious dance of alternating love and hate. 

Can it be there are two kinds of electricity ? This 
is the fact. One of these is obtained by rubbing- 
glass and it first received the name of vitrious (glass) 
electricity. For convenience we call it now positive 
electricity. The other kind was first called resinous 
electricity. We now call it negative electricity. When 
we charged the feather from the glass it was loaded 
with positive electricity or the same as on the glass. 
Then the feather was repelled. Are we not arriving 
at a law in this matter ? Positive electricity repels 
positive electricity. 

When the feather flew to the hand, or the bits of foil 
fell back on the table, they simply discharged their 
positive electricity and Avere ready to take more. How r 
about the attraction to the sealing wax ? Is its elec- 
tricity of another kind ? Yes. We are getting at the 
truth very fast. One more step and we are all right. 
The feather charged with positive electricity flew to 
the sealing wax because the electricity on it was neg- 
ative. 

Repeat the experiments carefully. Charge the 
feather with one electricity, and it is repelled. Charge 
it with the other, and it is attracted. Discharge it, 
and perform the experiment the other way, and the 



LIKE REPELS— UNLIKE ATTRACTS. 37 

same results are observed. Let one person charge the 
feather with positive or negative electricity, and then 
at once let another person, who has not seen the charg- 
ing of the feather and who does not know which it is, 
try it with the glass. If it is attracted by the glass 
(positive), the electricity of the feather is negative ; if 
repelled, it is positive. So we have this great law: 
Positive attracts negative, and repels positive. Negative 
attracts positive, and repels negative. Like repels; 
unlike attracts. 

Our bit of feather suspended by a silk thread, may 
seem a trifling affair, yet it teaches a great law in 
nature, a law which governs the lightning in the heav- 
ens, and, doubtless, affects that great star we call the 
sun, the worlds which swim round it, and the 
most distant star-dust lost in the interstellar spaces 
of the sky. On the knowledge of this law depends the 
success or failure of all our work in electricity, and 
until the law was recognized and understood, there 
could be no telegraphs, telephones, nor electric lights. 

By these simple experiments, we ask questions of na- 
ture, and learn from common things some of the great 
principles which govern the Universe. 

You charge the electroscope and its two drooping 
leaves fly apart, showing the presence of one kind 
of electricity. This explains its action when you used 



38 FIRST STEPS IN ELECTRICITY. 

it in other experiments. Then it was used merely to 
test the presence of electricity. It can also be used to 
tell whether any electricity whose presence it detects 
is positive or negative. 

It is the same with the paper tassel. Every ribbon 
is filled with electricity, and each repels the other till 
they stand out in every direction. The bit of tin-foil 
which leaps up to the electrified glass in your very first 
experiment charges itself, and is repelled, but the in- 
stant it touches any conductor, it is discharged and is 
free to be attracted again. The feather on the silk 
thread cannot discharge itself, and is repelled till 
brought near electricity of the opposite kind. 

So far you have demonstrated by your experiments 
that one of the manifestations of electricity is attrac- 
tion, and that this attraction is between an electrified 
body and one not electrified, and between opposite 
electricities. We have learned that electricities of a 
like character repel each other; that there are con- 
ductors and non-conductors; and that, by means of a 
long conductor supported by non-conductors, electrical 
effects can be obtained at a great distance. 

Otto Von Guericke,* of Magdeburg, was the first to 

*" Otto Yon Guericke." (1602-1686). A German philoso- 
pher, the inventor of the air-pump and a species of barometer. 
He was well known as an astronomer, and was the first to 



LIKE REPELS— UNLIKE ATTRACTS. 39 

observe the repulsion caused by electricity. Du Fay 
first made the experiment of attracting and then re- 
pelling a gold leaf floating in the air, and first made 
known this law of the effects of positive and negative 
electricity. 

teach that the return of comets might be fixed upon. He ad- 
vanced the theory of the two kinds of electricity. He also 
gave great labor and time to the study of botany. 



CHAPTER III. 

IKDUCTIOST. THE EGG EXPERIMENTS. THE ELECTR0- 
PHORUS. THE LEYDEN-JAR. 

All the experiments that you have performed will be 
helpful in trying others. If the new experiments you 
are now to take up seem complicated, go over carefully 
all that you have done before, and we shall have no 
trouble in understanding them. 

Your experiments have already demonstrated that 
electricity may be excited by the friction of silk upon 
glass, or flannel upon sealing wax. You also observed 
that electricity is conducted by copper, and that it can- 
not be conducted by silk. Eefer again to your list of 
conductors and non-conductors, as we shall now use 
both. The experiments demonstrated that the positive 
electricity from glass attracts the negative electricity 
of wax, and vice versa. Our experiments have shown 
us the law of attractions and repulsions — like repels, 
unlike attracts. Commit this law to memory for we 
must now use it as a key to new laws. 

Get the small feather and fine silk thread we used 

40 



KEW EXPERIMENTS. 41 

before, and suspend the feather by the thread from a 
gas lamp or other piece of furniture over the table and 
in easy reach. It will be found here that a pith ball, 
such as is included in the electrical outfit, is better 
than the feather. However, if you have none, use the 
feather. Have the board laid on the table, and warm 
the glass tube and the sealing wax and the two pads. 
Eub the glass briskly, and bring it near the feather. 
The feather flies to the glass, touches it, and is then 
repelled. The feather is now charged with positive 
electricity. It is said to be polarized. Eub the glass 
again without delay, and then, spreading the silk pad 
open, bring it near the feather. The feather flies to 
the pad. It is plainly attracted. If you fail, repeat 
the whole experiment, first polarizing the feather from 
the glass, till you see this attraction of the feather to 
the pad. 

Never give up an experiment and say it will not 
work, because you fail to get the results expected. 
Distrust yourself before you distrust nature. We ap- 
ply our law of attraction. If the positive feather is 
attracted, the pad must be negative. Use your imagi- 
nation always in these experiments. Try to imagine 
the condition of things. The feather, you see, is posi- 
tive. It was polarized by the glass. It flies to the 



42 FIRST STEPS IN ELECTRICITY, 

pad. There is only one conclusion. The pad must be 
negative. 

Discharge the feather by holding it in the hand 
for a moment, and then repeat this whole experi- 
ment, using the wax and the flannel pad. This ex- 
periment confirms the other, and the flannel pad is 
proved to be positive. Clearly here is something new. 
Friction excites electricity, and the electricity found 
in the two things rubbed together is of opposite polar- 
ity. If one is positive, the other is negative. The 
whole subject is becoming more curious than ever. We 
are evidently close to a n~ew aspect of the matter. 

What is electricity ? Is it anything that can be torn 
apart by friction ? We certainly have friction, and, as 
a result, positive electricity and negative electricity. 
In one case the positive is on the glass, in the other, 
the negative is on the wax. The silk pad is negative, 
the flannel is positive. What is this singular thing 
that behaves in such a peculiar manner ? This ques- 
tion has been a puzzle for a long time. We may ask 
what is water, and get a good answer quickly enough. 
No one is yet able to give as good an answer to the 
question before us. We can only say it is a result or 
manifestation of force. We use force and get friction 
and attractions and repulsions, but this does not tell us 
what electricity may be. 



FRANKLIN'S IDEA. 43 

Benjamin Franklin tried to give a reasonable expla- 
nation of what we have just seen. He imagined that 
everything contained a curious, invisible fluid, and that 
when there was too much of this fluid present in any- 
thing, it displayed positive electricity; when it had too 
little, it exhibited negative electricity. This seemed a 
good notion, because by friction the regular supply of 
the fluid was upset, and too much or too little appeared. 

Others have imagined that there might be two invis- 
ible fluids, and that when both were present, nothing 
happened, and no electricity could be found. By fric- 
tion they could be pulled apart. When drawn apart, 
they attracted each other and pulled light bodies after 
them, as we have seen in our experiments. If two bod- 
ies held a fluid of the same kind, they repelled each 
other. 

The question is not settled. Nobody knows whether 
there are such fluids. It is quite possible they do not 
exist at all. However, this notion that there are two 
fluids, whether true or not, will help us to understand 
our experiments. We call it a working notion, and we 
shall use it as an imaginary tool in our future experi- 
ments. Many people have thought that imagination 
was something to be regarded with mild disapproval as 
just a little vain and foolish. For such work as this, 
the Creator has given us in a vivid imagination one of 



44 FIRST STEPS IX ELECTRICITY. 

the best mental tools we can use, and the wise stu- 
dent takes pains to cultivate it. We may now go on 
to quite a different matter, and remembering this work- 
ing notion try to use it as a tool in explaining new 
experiments. 

Get a small stick of pine wood, a yard-stick, or 
a wooden ruler. Hang up the feather by the silk thread 
and place the table under the feather. Have the 
thread long enough to bring the feather within about 
five inches of the table. On the table place a tumbler or 
wineglass upside down, and on the tumbler lay the stick 
so that it rests even and quiet. Then push the glass 
and the stick toward the feather till the feather hangs 
opposite one end of the stick. If the stick is too low 
place books under the glass till the feather hangs 
directly opposite the end of the stick, but not touch- 
ing it. Excite the glass tube and then hold it over the 
opposite end of the stick without touching it. At 
once the feather is attracted to the stick, swings 
toward it, touches it, and is then repelled. This looks 
very much as if the wooden stick on the insulated 
stand was acting as a conductor, conveying the positive 
electricity to the feather and charging it till it shows 
repulsion. Take the tube away from the stick and all 
the electrical effects disappear. This is certainly queer 
and quite unlike anything we have found before. 



THE EGG EXPERIMENT. 45 

Kepeat the experiment to make sure you observe all 
that happens. After the experiment is finished bring 
the tube near the feather and it is attracted. It is clear- 
ly not positive and obtained no electricity from the glass 
through the stick. Touch the stick with the excited 
glass and watch the effect. The stick is clearly charged 
and produces a marked effect on the feather. To 
understand this matter let us try other experiments. 

Put an egg on its side on a small wineglass, get the 
electroscope and place these on the table near the sus- 
pended feather. Kub the glass tube, and hold it near 
one end of the egg. Observe that the egg is insulated, 
and whatever electricity is in it cannot escape. (Note. 
The egg, glass, and tube should be warm and dry.) 
Now, on the notion of the two fluids, what happened 
to the egg when the rubbed tube was brought near it ? 
Nothing whatever is visible. We cannot see that any- 
thing happened and we must try to imagine what 
happened. We first imagine it holds electricity just 
as everything not in any way electrified by friction or 
other means holds it, in equal proportions of positive 
and negative. Kemember our law, positive attracts 
negative. When the positive tube comes near the egg 
all the unlike or negative electricity in the egg is at- 
tracted to one end of the egg, as if to meet it. All the 
positive, on the other hand, tries to fly away from it. 



46 FIRST STEPS IN ELECTRICITY. 

Neither can escape owing to the insulator (the wine- 
glass), so all the negative gathers at one end as close 
to the positive tube as it can get, and the positive 
gathers at the opposite end as if trying to get as far 
away as possible. Take the tube away, and, lifting the 
wineglass, bring the egg near the feather and the 
electroscope. Xot a trace of electricity can be found 
in the egg. 

Kepeat the experiment, and while the tube is still 
held close to the egg, bring the electroscope near the 
egg. Instantly it shows the egg is well charged with 
electricity. Take the tube away, and it is gone. 

It is easy to imagine just what happened. The 
two electricities were pulled apart. When the tube 
was removed, they flowed together again. We im- 
agined they collected at the ends of the egg when 
the tube was near. Can we prove this ? Here you 
must notice that in this experiment, and in the experi- 
ment you performed just now with the insulated stick 
of wood, the excited tube is not allowed to really touch 
the stick or the egg. This effect, caused by bringing 
an electrified body (the glass) near an unelectrified 
body (the egg), is said to be produced by induction. 
When by friction the glass is made positive it has the 
power to attract the negative electricity in anything 
near it. This power is called the power of induction, 



INDUCTION. 47 

and all the effects we see are said to be caused by 
electrical induction. 

Can we prove that there is this separation of the 
electricities in the egg by induction? Hold the ex- 
cited tube near the egg. We can imagine the positive 
is now all at the opposite end and the negative all gath- 



No. Yin. 

ered close to the tube. Now, while the egg is thus 
subject to induction and the tube is still held near 
the egg, gently touch the opposite end of the egg with 
the knuckle and then draw the hand and the tube 
away. Eaise the glass quickly and test the egg with 
the electroscope. The egg is highly electrical. To 



48 FIRST STEPS IX ELECTRICITY. 

understand just how the work is done look at Picture 
No. VIII. 

One more step and we shall solve the puzzle. Dis- 
charge the egg, the electroscope, and the feather by- 
touching them, and begin the experiment by bringing 
the rubbed tube near the feather till it is polarized or 
made positive, and is repelled. Now quickly rub the 
tube, and bring it near the egg, touch the opposite end 
as before, and then take aw T ay the tube. Lift the egg 
by the glass and bring it near the positive feather. 
The feather flies to meet it. Unlike attracts — the egg 
is negative. 

Try to imagine all that happened. By induction 
the negative electricity in the egg was drawn to 
one end, and the positive was repelled to the other 
end. A touch of the finger allowed the positive to 
escape and leave the negative alone on the egg. When 
the tube was removed, the negative flowed all over the 
egg and covered it completely. 

Discharge everything, repeat the whole experiment 
wdth the sealing wax, and prove the work. 

Our experiment with the pine stick and feather 
was just like this experiment. The positive glass by 
induction drew all the negative electricity in the stick 
to one end, and the positive flew to the other end and 
at once attracted the feather. Now we can imagine 



INDUCTION. . 49 

this as happening in everything near the positive glass, 
but in order to prove it we have to insulate the stick 
or the egg we use in the experiments, otherwise the 
negative might gather near the glass, but the positive 
would fly off somewhere and we could not find it. 
Only by insulation can we keep the electricity together 
long enough to enable us to see how it behaves. 

Next, get one more egg and another wineglass and 
you may repeat the experiment in another way. Place 
the eggs, each on a glass as before, side by side, 
the two eggs just touching each other. Rub the glass 
and place it near one of the eggs. This is plainly 
shown in Picture No. IX. 

While the tube is in that position, gently draw the 
second wineglass away to separate the eggs, and then 
remove the tube. Try to imagine what has hap- 
pened. The two eggs touched each other and prac- 
tically made one. The negative electricity of both 
gathered near the tube. The positive of both gathered 
at the distant end of the second egg. By drawing 
them apart we collected the positive in one egg, and 
the negative in the other. 

See that all is discharged, and begin again, first 

polarizing the feather. Hold the egg pulled away 

near the feather, and observe what happens. Try the 

other egg with the feather. In this way prove 

4 



50 



FIRST STEPS IN ELECTRICITY. 



beyond dispute that all we imagined as taking place 
really did take place. Eepeat the whole experiment 
with the sealing-wax, and prove which egg is pos- 
itive and which is negative. Depend wholly on your- 
self. Settle everything by actual trials repeated at 




No. IX. 



least twice, and put down the results in your note- 
book for future reference. 

Having obtained a clear idea of this singular matter 
of electrical induction, we can go on to other and 
even more interesting experiments. Get a circular 



THE ELECTROPHORUS: 51 

piece of thin vulcanite * about six inches in diameter, 
and fasten it to a round piece of dry wood with small 
tacks. Get also a circular piece of tin-plate about four 
inches in diameter. Heat the centre of this plate over 
a lamp, and when quite hot press the end of a stick of 
sealing wax against the plate. It will melt, stick fast, 
and, when cold, form an insulated handle. It will also 
be an improvement to fasten a round brass button or 
round bit of metal to the edge of the plate with a 
drop of sealing wax. Such an apparatus is called an 
electropliorus, and a similar apparatus, except that the 
handle is made of glass, is shown at the left in Picture 
No. X. 

In some apparatus the handle of the tin-plate 
of the electropliorus is of glass and it can be used 
in place of the glass tube by unscrewing it from the 
plate. With such an apparatus you can perform nearly 
all the experiments already done, besides many more 
that will be quite as curious and instructive. 

Warm the vulcanite plate of the electropliorus and 
then rub it hard with the flannel pad. Then lifting 

* 1. " Vulcanite." Called also ebonite. India-rubber 
which, by a process called vulcanization, has been rendered 
hard like horn. This condition is brought about by combin- 
ing the caoutchouc with sulphur by means of a very high tem- 
perature, — a process discovered by Prof. Goodyear. 



52 



FIRST STEPS IN ELECTRICITY. 



the tin-plate by its handle lay it on the vulcanite. Lift 
it off and test it with the feather and the electroscope. 
No effect. Placing it on the rubbed vulcanite, which 
you may be sure was well charged by the friction, does 
not appear to affect it. It is clearly neutral or non- 




electrical. Put it back on the vulcanite, and while it 
rests there, touch the upper side quickly and gently 
with the finger. Now lift it and test it with the elec- 
troscope. It is highly electrical. Put it back on the 
vulcanite and touch it as before. It is again strongly 



THE ELECTROPHORUS. 53 

charged with electricity. In the electrophones we have 
a practical electrical machine, for we can lay the plate on 
the vulcanite, touch it, and lilt it off well charged with 
electricity for twenty or thirty times after once rubbing 
with the flannel pad. 

Try to imagine what happens in this apparatus. It 
is plainly induction. On rubbing the vulcanite it is 
electrified and made negative. On laying the plate 
upon it the positive electricity of the plate is attracted 
to the under side, and is said to be bound. The nega- 
tive is repelled and collects on the upper side, and is 
free to escape to the finger as soon as the plate is 
touched. For this reason it is called free electricity. 
Then on lifting the plate you find it contains only pos- 
itive electricity. 

Charge the feather with the tube as before, and 
repeat this experiment. Hold the plate to the feather. 
It is repelled, and the experiment proves that all 
we imagined took place really did take place. The 
plate can therefore be used in place of the glass 
tube in repeating all your previous experiments at a 
great saving of labor, because when once rubbed the 
vulcanite will act by induction on the plate many times 
over. 

Take the electrophorus to a dark room, rub it briskly, 
put on the plate, touch it, then lift it by the handle, 



54 FIRST STEPS IN ELECTKICITY. 

and bring your knuckle near the button on the plate. 
There is a slight snap or cracking noise, and a tiny 
spark flies between the plate and hand, leaving a sting- 
ing sensation. Eepeat this as many times as you wish, 
because it shows us Avholly new phenomena. Electric- 
ity now manifests itself as light, as sound, and as a 
physical sensation. You can see, hear, and feel it. 

Here is clearly something different from the attraction 
or the repulsion, the polarity, conduction, or non-con- 
duction, or the induction we demonstrated by your ex- 
periments. The whole matter increases in interest, 
and we want to go on, to see, and to learn more. You 
now need something to enable us to keep electricity 
when we get it. 

At the right in Picture No. X. is shown another 
apparatus easily made of cheap materials. Select a 
smooth glass tumbler, getting the best quality of cut 
glass. Make some flour paste and get a little common 
tin-foil. Then line the inside of the tumbler with the 
foil, covering the bottom and sides up to an inch of the 
top. Cover the outside also with foil to the same 
height, using the paste to keep the foil in place both 
outside and inside. Get a piece of stout copper wire, 
bend the lower part to form a little foot, and resting it 
on the foil inside the tumbler fasten it upright in that 
position with hot sealing wax. Then to the top fasten 



THE LEYDEX-JAR. . 55 

with the wax a common brass button. All this is 
plainly shown in Picture No. X. See that it is well 
dried before a fire or in the sun, and then place it on 
the table with your electrophorus. Eub the vulcanite 
plate briskly, lay the tin-plate on it, touch the upper 
side gently, and then lifting it by the handle bring the 
little knob on the edge of the plate close to the button 
at the top of your new apparatus. There is a little 
snap and a tiny spark flies between them. Eepeat this 
ten or twenty times in succession, placing the tin-plate 
on the vulcanite, touching it and holding it to the but- 
ton to see the little spark. 

Now take the tumbler in one hand, holding it by the 
tin-foil on the outside. Then touch the button on the 
wire with the other hand. The effect is surprising and 
peculiar. It may startle you, but while it stings for an 
instant it is perfectly harmless. It seems exactly as if 
we had loaded up the tumbler with a series of little 
sparks and then drew it all out in one big spark. Try 
it another way. Load it up again from the electropho- 
rus and then let one person hold it in one hand while 
he gives the other hand to another person, and let this 
second person touch the top of the wire. Both feel the 
effect through their arms. 

Let us try to imagine what happened in the tumbler 
during this experiment. The plate by induction held 



56 STEPS IX ELECTRICITY. 

free negative on the upper side as it rested on the vul- 
canite. You withdrew all the negative electricity when 
you touched it. On lifting the plate it held only posi- 
tive electricity. On bringing it near the wire of your 
new apparatus the positive leaped across to the button 
and escaped down the wire to the tin-foil in the tumbler. 
Each time you repeated this there was a rush of posi- 
tive electricity into the foil. You know like repels — 
unlike attracts. There was both positive and negative 
in the foil. The negative attracted the positive in the 
plate, and it being free and alone crossed over to meet 
its mate in the tin-foil. The negative in the foil 
also sprang across at the same instant into the 
plate. The two electricities crossed in their effort to 
equalize each other and be together. The whole proc- 
ess was repeated each time with this curious result. 
You continually removed the negative from the plate 
and it was restored by taking from the foil. The posi- 
tive, on the other hand, could not get away from the 
foil because it was surrounded by the insulating glass 
of the tumbler. Thus it happened the inside foil was 
drained of its negative, and loaded up with more posi- 
tive than it wanted. 

During all this you can well imagine something must 
have been going on in the foil on the outside of the 
tumbler. Induction was here at work also. The two 



THE LEYDEX-JAE. 57 

foils were separated by the glass walls of the tumbler, 
yet induction acted across or through the glass. The 
inside foil, being strongly positive, by induction at- 
tracted all the negative of the outside foil and it gath- 
ered next the glass. It was very much as if it wanted 
to get through, but could not and so kept on that side 
as close to its companion as possible. The positive, on 
the other hand, was repelled and escaped in every direc- 
tion into the table or any other conductor in reach. 
To help it get away it is a good plan to put the tumbler 
on a piece of wire that reaches to the floor or to the 
nearest gas or water pipe. 

Xow you have a curious state of affairs. Here are 
the two electricities close together, yet kept apart. 
Give them a chance and they will rush together with a 
loud snap and a bright spark. Let them use your 
hands and arms as a conductor and they flow together 
with a shock. They are of opposite polarity — iinlike 
attracts — and you are pretty well aware of the vigor 
with which they rush together through your tingling 
fingers. 

To prove all this place the tumbler on a small piece 
of window glass. If this is not convenient get four 
tumblers, warm them thoroughly and place them up- 
side down on the table and lay a dry board or a book 
on them. This will make a little insulated table that 



58 FIRST STEPS IN ELECTRICITY. 

you can use in place of the sheet of glass. Then twist 
some fine copper wire round the top of the electroscope, 
and lay the other end on the insulated table and fasten 
it down by placing the tumbler on it. The outer tin- 
foil is now connected with the leaves of the electro- 
scope, and the instant we begin to charge the inside 
foil from the electrophorus the electroscope indicates 
the presence of the electricity driven off from the outer 
foil. 

The apparatus you have been using is called a con- 
denser or Leyclen-jar. When first used it was regarded 
with mingled horror and amazement. People thought 
it bewitched, and spoke of it with solemn awe as some- 
thing just a little wicked and unnatural. It was first 
described by Kleist, of Cammin in Pomerania, in 1745. 
A year later, Cumeus, of Leyden, also discovered 
how to make one, and thus it got the name of Leyden- 
jar. Musschenbroek, * the savant (1692-1761), felt a 
shock from a jar and declared nothing would ever 
tempt him to try it again. Boze, another savant (1723 
-1788), declared he would willingly die of the shock, so 
great did he regard the doubtful honor of being killed 

* " Musschenbroek" (1692-1761). A Dutch mathematician. 
He adopted the Newtonian system of philosophy, and helped 
introduce it into Holland. He held the chair of mathematics 
at Leyden for several years. 



THE LEYDEN-JAR. 59 

by such a truly wonderful and awful machine. Dr. 
Watson * and Dr. Bevis both improved it, and Frank- 
lin made it the subject of some researches and discover- 
ies that were, at the time, thought to be very wonderful, 
Tyndall, of London (born 1820), invented some of the 
experiments you have tried with the Leyden-jar and 
the other apparatus, and greatly aided all students of 
this great science, who, like ourselves, wish to under- 
stand this complicated matter of induction. 

* " Dr. Watson," Richard. (1737-1816). An English prelate. 
He was professor of chemistry in Cambridge. 






CHAPTER IV. 

THE CONTIGUOUS INDUCTION MACHINE. THUNDER- 
STORM EXPERIMENTS. FRANKLIN^ BRAVERY IN 
THE PURSUIT OF KNOWLEDGE. 

Select a dry evening when the air is clear and cold, 
and let us examine this matter of the behavior of elec- 
tricity a little closer. If the weather is warm or wet, 
be sure and have the room in which you work dry. 
Get the electrophorus, the Leyden-jar, and other appa- 
ratus, wipe off all dust that may be on them, and warm 
them before a fire or over a lamp. 

Let us begin with the electrophorus. See that the 
vulcanite and the flannel pad are warm and then rub 
briskly for a moment to electrify the vulcanite. 
Then put the tin-plate on it, touch it with the finger to 
draw off the free negative. Bring the knuckle near the 
button on the edge. The little spark appears. Try it 
on the Leyden-jar and the electroscope. Everything 
works well and you can go on to new work. 

Get a shoe-buttoner, a hair-pin, and a large needle 
or one of the long sharp pins used by ladies for hat-pins. 

60 






POINTS AND KNOBS. 61 

Prepare the electrophorus and then take the shoe-but- 
toner in the hand, resting one finger on the steel part, 
if it has an ivory or other handle. Present the rounded 
end to the little button on the plate and a bright spark 
appears. Try the hair-pin, using the rounded end and 
holding it by the two points. Again a bright spark 
with some noise. Now turn the hair-pin round and 
present the points to the plate. Nothing happens. 
There is neither flash nor sound. Turn the lights 
down and repeat the experiments several times. Even 
in the dark only a very small spark can be seen. Try 
the needle or pin. No apparent results. It seems as 
if the electrophorus had completely failed. Try it 
with the knuckle or the shoe-buttoner and you will 
find it gives just as good sparks as ever. Fasten a fine 
copper wire to the button on the edge of the tin-plate, 
and connect the other end with the electroscope. Kub 
the vulcanite as before and put the plate on it, and 
then, without touching it, move it up and down an 
inch or two by the handle, and at every movement the 
leaves of the electroscope will rise and fall, plainly 
showing the presence of free electricity. 

The experiments with the pins and the shoe-buttoner 
remind us of conduction. Let us consider this for a 
moment. The button er, hair-pin, and needle are all 
good conductors, and yet the electricity behaves in a 



62 FIRST STEPS IX ELECTEICITY. 

different way with each. Has it anything to do with 
the shape of the conductor ? Observe the conditions 
of our experiments. "We used rounded surfaces and 
points. With the rounded surface, like the knuckle or 
the round part of the hair-pin, there is a spark. With 
the points there was nothing to be seen or heard. We 
are reaching a new law in conduction : Pointed conduc- 
tors carry electricity through the air in silence. With 
rounded surfaces the electricity flies across the little air 
space with light, heat, and sound. Points not only 
conduct electricity in silence, but act very quickly. 

It is well to prove things by other experiments. Get 
a sheet of soft tissue paper, fold it up and cut it into 
strips so that when unfolded it will make a tassel. 
Fasten it to a hair-pin, and hang it up by a silk thread. 
(See Picture No. VI.) Charge it from the glass tube 
as in the former experiments or better from the electro- 
scope till the tassel stands out in every direction. It 
has now electricity of one polarity, and as like repels 
like, every thread of the tassel stands out from every 
other. Next bring the closed hand or the knuckle un- 
der the tassel, but not near enough to touch it. If the 
hand moves the whole tassel follows it, but unless act- 
ually touched and fully discharged, the tassel is as stiff 
as ever. Now hold the long, sharp pin, or the needle 
in the hand under the tassel, point upward, and near 



POINTS AS CONDUCTORS. 63 

the centre. At once the tassel is discharged and the 
threads collapse. The sharp-pointed conductor in- 
stantly carries off the electricity where the rounded 
knuckle failed to remove any of it. Points are plainly 
silent conductors, and very good conductors. This you 
should note down and remember as part of the law of 
conduction. 

Let us return a moment to our electrophorus. We 
rub the vulcanite with flannel and then lay the tin- 
plate upon it. You know from former experiments 
just what has happened. By friction the positive elec- 
tricity is drawn off to the flannel, and the negative re- 
mains on the vulcanite. By induction, as illustrated 
by the experiments with the eggs, the positive electric- 
ity in the plate is attracted to the under side where it 
becomes bound, and the negative is driven to the upper 
side where it is free to escape the instant it is touched 
by any conductor. On lifting the plate the positive 
electricity flows all over it. 

We cannot see anything of this. We use our imag- 
ination and see it in the mind. Experiments prove 
that our mind-picture is correct. On bringing the 
plate near a conductor the electricity seeks to equalize 
itself, and breaks through the air to meet the negative 
electricity in the knuckle or other conductor. There 
is a transfer both ways, positive to the finger and neg- 



64 FIRST STEPS IN ELECTRICITY. 

ative to the plate, and the plate is once more neutral or 
balanced, with both positive and negative in equal 
quantities. Put the plate on the vulcanite, and the 
whole process can he repeated many times. We make 
this little review of our work because it leads us to 
another kind of electrophorus. 

Naturally the electrophorus is such a capital appara- 
tus for your work and experiment, you might ask if 
there are no improvements to be made in it. It has 
been improved, and there are now several forms of con. 
tinuous electrophorus, or machines giving a' constant 
succession of electrical effects by induction. 

Picture No. XI. represents a small cheap contin- 
uous electrophorus often used in schools. It con- 
sists of a round sheet of glass called the plate, 
supported on an arbor so that it may be turned 
by a hand-crank. Near the lower edge are two 
silk cushions or rubbers designed to press against the 
glass as it is turned around. At one end of the stand 
is a wooden upright, carrying an insulated standard of 
brass having a round knob at the top. From this part 
a brass arm extends along the side of the plate which 
is armed with a row of points that nearly touch the 
glass. This brass arm and standard are called the 
prime conductor. Between the prime conductor and 
the rubbers is suspended a silk bag enclosing a quarter 



THE CONTINUOUS INDUCTION MACHINE. 65 

part of the plate. This makes an induction machine 
that is continuous. By turning the crank a continu- 
ous stream of sparks can be obtained from the prime 
conductor as long as the plate revolves. Such an ap- 
paratus is another form of electrophorus and is com- 
monly called an electrical machine. 




No. XL 
Eecalling our past experiments in induction let us 
try to understand the theory of this machine. Here 
are silk rubbers pressing on glass, and, as we know 
from our experiments with the tube, separating the 
electricity, sending the positive to the glass and the 
5 



66 FIRST STEPS IN ELECTRICITY. 

negative to the silk. That part of the plate thus excit- 
ed moves on, as it turns, between the sides of the silk 
bag until it reaches the row of points on the prime 
conductor. Here induction takes place and the nega- 
tive of the prime conductor streams from the points to 
the glass, leaving the free positive behind. The nega- 
tive unites with the positive on the glass plate and 
balances it until, in turning, it meets the rubbers. 
Here by friction it is separated and the negative flies to 
the rubbers and escapes down the metal supports. 
As the plate moves on, the whole process is repeated 
continuously, and thus the machine becomes a contin- 
uous electrophorus. 

Larger machines have two or more sets of rubbers 
and are sometimes very complicated, yet by the aid of 
your experiments with simple things you are able to 
readily understand the most complex machine you may 
meet in any future studies. Observe, however, that we 
here produce free positive electricity, while from the 
plate of the electrophorus we take free negative electric- 
ity. The result is precisely the same except in the 
polarity of the electricity. To ascertain the polarity 
of the machine use your glass rod and silk pad, and 
charge the little feather hanging by the silk thread till 
it is repelled, which proves its polarity is positive. 
(Consult your note-book about this.) Now turn the 



THE CONTINUOUS INDUCTION MACHINE. 67 

crank of the electrical machine and holding the feather 
by its thread bring it near the prime conductor. It is 
still repelled — like repels like. This test must be made 
carefully and quickly to get the best results. 

In using the machine, turn the crank with the right 
hand and place the left on the base of the machine 
resting against one of the metal pieces that support 
the rubbers. This will keep the machine steady and 
allow the negative electricity to escape through your 
hand and body to the ground. Unless some conductor 
is thus arranged, the machine works badly. 

Turn the crank quickly ten times while some one holds 
the knob of your Leyden-jar to the prime conductor. A 
stream of small sparks will flow to the jar. Discharge 
the jar by holding it in one hand and touching the knob 
with the other hand. Another way is for one person 
to hold the jar and join hands with several others, the 
last person touching the knob. If the weather is 
favorable for work this will be probably as shocking a 
surprise as your friends will care to experience. A 
stronger charge in the jar might prove unpleasant, and 
you must make a discliar ger. Get a piece of copper 
wire, of medium size, about ten inches long. Eoll up 
the ends into little knobs and bend it into a half circle. 
Set fire to the end of a short piece of sealing wax and 
press it against the middle of the copper wire. When 



68 FIRST STEPS IN ELECTRICITY. 

the wax is cold it will form an insulating handle for 
the wire. This is called a discharger. 

Turn the handle of the machine briskly and hold the 
jar to the prime conductor. If working alone, a good 
plan is to connect the top of the jar with the prime con- 
ductor by a copper wire. The jar can then be filled 
quickly and silently. Now place one end of the dis- 
charger against the side of the jar (always hold it by the 
handle) and bring the other end near the knob. At 
once there is a vivid flash as the two electricities flow 
together. Repeat the experiment in the dark. Tiny 
sparks of fire will be seen streaming from the points of 
the prime conductor and running about inside of the jar 
when it is being filled by holding it near the machine. 
Besides the flash when the jar is discharged there will be 
also a brilliant ring of fire inside the jar. 

It may be noted here that our Leyden-jar is a small 
one. A larger jar would hold more and give larger and 
louder sparks. Instead of one large jar you might use 
several at once. Four or more jars like the one you 
have made can be placed on the insulated table or on a 
sheet of glass and the wires be all connected by a piece 
of copper wire. Another piece of wire must be tied 
round the outside foil of all of them. This would 
form a battery of jars and give very large and powerful 
effects. They could be arranged in another way, in- 



FRANKLIN'S EXPERIMENTS. 69 

vented by Franklin. Get two jars and place them on 
the insulated table, then connect with a wire the bot- 
tom (outside) of one with the top of the wire of the 
next. You can easily imagine what would happen 
now. By induction the free electricity of one jar 
drawn off by induction from the outside foil would es- 
cape through the wire into the next jar, there to again 
produce induction. Franklin arranged several jars in 
this way and called the apparatus a cascade battery. 

With your electrical machine, Leyden-jar, and dis- 
charger you can now perform a number of electrical 
experiments. Cut some Dutch metal into bits a quar- 
ter of an inch long, and paste these in a row across the 
bottom of a flat tumbler. Put the pieces on the glass 
about a sixteenth of an inch apart. When dry put the 
finger on one end of the line of pieces of foil and bring 
the other end near the prime conductor of the 
machine while the crank is turned. In the dark a 
pretty stream of fire will be seen playing along the 
spaces between the pieces of Dutch metal. 

Warm four glass tumblers and place them upside down 
on the floor and lay a board over them. Let one person 
stand on the board and rest his hand on the prime 
conductor, while another turns the crank rapidly. 
Curious effects will be seen in the way the hair stands 
erect on the head. Any one touching the face or 



70 FIRST STEPS m ELECTRICITY. 

hands of the person on the insulated stand can draw 
a spark. With a little practice the person on the 
stand can also light a gas jet with a touch of the fin- 
ger. Another experiment is to charge the jar and 
then, holding a piece of letter paper near the knob, 
use the discharger to send a spark through the paper. 
It will make a minute hole in the paper. 

So far in our work you have demonstrated by your 
experiments that electricity attracts and repels, that 
it has polarity, that like polarity repels, unlike at- 
tracts. You showed that it can be conducted and 
that there are conductors and non-conductors, and that 
there is a difference between rounded and pointed sur- 
faces in their power of conduction. You have also 
demonstrated the behavior of electricity under con- 
duction, which is really a mode of action under the 
influence of attraction and repulsion. 

It seems almost strange that this great science can be 
reduced to so few, simple, and easily remembered laws. 
This is one of the grand features of nature. The great- 
est results are produced by the most simple laws. These 
laws when understood explain the most marvellous exhi- 
bitions of power in nature. It is by these laws the four 
phenomena you observed when we began our studies 
are explained. The crackling sounds in the girFs 
hair as she combed it out, the sparks in the cat's fur, 



ATMOSPHERIC ELECTRICITY. 71 

the sticky behavior of the lint on the dress all came 
from frictional electricity. Even the lightning fol- 
lows the laws of induction. 

We noticed that by induction electricity may be 
bound or held. This has led to a special name for 
the electricity we have been considering, and it is 
called static electricity. It is also called frictional 
electricity and, as it can always be found in the air, 
it is sometimes called atmospheric electricity. There 
is free positive or negative electricity in the air at all 
times. It comes from the friction of the air on the 
earth or, as we shall see by other experiments, is ex- 
cited by other means. Its grandest display is in the 
lightning. 

A cloud moves over the earth in the air, and 
from friction or some other cause becomes posi- 
tive. By induction the negative electricity in the 
earth rises to meet it and follows trees, houses, or 
other tall objects to get as near the positive cloud as 
possible. If the mutual attraction is strong enough a 
flash leaps through the air as the electricities come 
together. 

A cloud may be positive or negative, and ap- 
proaching another cloud, act by induction, drawing 
the opposite electricity to the side nearest to it and 
holding it there, leaving the free electricity to escape 



72 FIRST STEPS IN ELECTRICITY. 

in a flash to still another cloud or to the earth. Per- 
haps the two opposite electricities unite with a flash 
and leave the free electricity to flash with a return or 
second stroke. Either of these effects of induction 
may take place whenever the clouds and the earth re- 
semble a huge Leyden-jar, as in a thunder-storm. 

A cloud appears and passes over a forest. Every 
point on every leaf conveys away the electricity, like 
the points in an electrical machine, in silence. The 
cloud moves on, perhaps still highly polarized, and 
passes over a house. Induction takes place; the house 
is polarized, and the opposite electricity not finding 
points enough from which it can stream off in silence, 
breaks from the house to the cloud with a terrible 
crash, and the house is destroyed or set on fire. A 
man seeking shelter under a tree is killed. His body 
is a better conductor than the tree, and the electricity 
moved by induction goes from the cloud to the ground, 
or from the ground to the cloud through the tree and 
then through the man, and the shock is so great his 
life is destroyed. It makes no difference what the 
polarity or direction of the flash as the effects are the 
same. The cloud may act by induction ; opposite 
electricities may unite or free electricity escape from 
the cloud to the earth or vice versa. 

It was an American who, seeing the relation between 



FRANKLIN'S BRAVERY. 73 

the conducting power of points and rounded surfaces, 
first applied it to atmospheric electricity. He tried in 
other ways the same experiments you have tried, and 
in writing about them he said: "If these things are 
so, may not the knowledge of this power of points be 
of use to mankind in preserving houses, churches, 
ships, etc., from the stroke of lightning, by directing 
us to fix, on the highest parts of those edifices, up- 
right rods of iron made sharp as a needle, and gilt, to 
prevent rusting, and from the foot of those rods a w T ire 
down the outside of the building into the ground, or 
down one of the shrouds of a ship and down her side 
till it reaches the water ? Would not these pointed 
rods probably draw the electrical fire silently out of a 
cloud before it came nigh enough to strike, and 
thereby secure us from that most sudden and terrible 
mischief ? " 

This man had the courage to put this to the test of 
a great and daring experiment. We can hardly un- 
derstand such magnificent courage in the pursuit of 
knowledge. Standing with his son in an open field, 
near what is now the corner of Kace and Eighth streets, 
^Philadelphia, he put up in a thunder-storm a silk 
kite. At the top was a sharp pointed wire. The kite 
string when wet by the rain was a conductor, and at 
the lower end was a piece of silk ribbon as an insula- 



74 FIRST STEPS IN ELECTRICITY. 

tor. On the string hung a key, and from this key- 
sprang to the man's hand the first spark that proved 
that the lightning was static electricity. We can 
well understand his courage when we learn that a year 
later another experimenter, Kichmann, of St. Peters- 
burg, repeating this experiment, with a tall pole in 
place of a kite, was instantly killed. To-day Frank- 
lin's experiment is to be seen in every lightning rod on 
spire or ship. 

Static electricity is used to light gas lamps in halls 
and churches by employing a small electrophorus or 
induction machine to give a spark. It is used also for 
moving light bodies in certain machinery, to fire great 
guns on ships, and to explode powder or dynamite 
in blasting. To understand the uses of electricity in 
other ways, we must go on to other experiments and 
continue our studies in other branches of this great 
science. 



CHAPTEE V. 

MAGNETISM. A SHORT CUT ACROSS ANOTHER FIELD 
OF SCIEXCE. 

Loxg years ago people, like ourselves, anxious to 
learn something of nature by asking her questions, 
found a certain iron-stone or iron-ore that had the 
singular property of attracting pieces of iron when 
brought near the stone. For some unknown reason 
such iron-stones received the name of loadstones. As 
some of this ore was found near the ancient city of 
Magnesia in Asia a better name was given *to it. 
Pieces of the ore were called magnets and this curious 
property of attraction was called magnetism. Still 
later the ore was called magnetic iron, all these terms 
being naturally suggested by the name of the old 
city. 

For centuries men seemed to be content to know 
this little and nothing more. Only in quite modern 
times did any one seek to learn more by experimenting 
with these loadstones or magnets. It is true, that 
many hundreds of years ago in China a use was found 

<0 



76 FIRST STEPS IX ELECTRICITY. 

for these magnets, but why these stones possessed this 
curious property no one seems to have cared to find 
out. The use made of magnets in China we shall 
learn presently. Just now we may notice that mag- 
nets have been known for a very long time, and yet it 
is only within a very few years that their greatest 
value was discovered. To-day there are thousands on 
thousands in daily use all around us and without them 
business would almost come to a stand-still. 

It was early found that if a piece of iron be rubbed 
on one of these loadstones it too would have the power 
of magnetic attraction and be a magnet. The bits of 
stone are not easy to use in our experiments, and we 
shall find it better to get a steel magnet. You can 
buy one for a small sum at the optician's or the 
maker of scientific apparatus. It was found that 
when common soft iron is rubbed on a loadstone to 
cause it to become a magnet, it in time loses its 
magnetic property and will no longer exhibit any 
trace of magnetism. Steel, on the other hand, will 
keep it for a long time. So it happened they were 
classified as natural magnets or loadstones, as temporary 
magnets, and permanent magnets. Your small steel 
magnet bent into the shape of the letter U is a perma- 
nent magnet, and from its shape it is commonly called 



MAGNETS. 77 

a horseshoe magnet. Magnets made of straight pieces 
of steel are called bar magnets. 

There is one other kind of magnet. This we shall 
examine a little later. In all this you may think we 
are travelling very far from studies in electricity. It 
seems so, yet we are really on the right path and shall 
return to electricity in the end. Just now we shorten 
the road by "cutting cross lots " through another field 
of science. 

Get the magnet, some small iron tacks or nails and 
some iron filings. Get also a sheet of stiff writing- 
paper. No special pains need to be taken about the 
temperature or dryness of the room and the experi- 
ments can be performed anywhere and at any time. 
The first thing you observe about the magnet is the 
piece of iron that comes with it, and that is usually at- 
tached to the two ends of the magnet. With a little 
effort it can be pulled off. There is no gum or paste 
on the magnet, and this clinging of the bit of iron to 
the magnet is not due to anything of that kind. The 
piece of iron is called an armature. Now take the 
armature in one hand and the magnet in the other, and 
slowly bring the armature opposite to the ends of the 
magnet. As it comes nearer there is a curious pull 
or attraction growing rapidly stronger and stronger till 
the armature jumps to the magnet and sticks fast. 



78 FIRST STEPS 1ST ELECTRICITY. 

Here is plainly a permanent attraction, and you notice 
that it is not caused by friction as in your electrical 
experiments. 

Take the armature off and try it on all parts of 
the magnet and you quickly prove that this mag- 
netic attraction or the attraction of magnetism is only 
at the ends of the magnet, which are called the poles. 
Take off the armature and try the magnet on the nails. 
The attraction is so strong that the nails can be lifted 
by the magnet though they may touch it only by the 
points or sharp corners. Pull the nails off and then 
try one on another. No effect. It is plain that the 
nail did not take any magnetism from the magnet or, 
if it did, lost it very quickly. Try the armature on the 
magnet. It is as strongly attracted as ever. It is 
plain enough that the magnet did not lose any magnet- 
ism while the nails were clinging to it, nor did it give 
its magnetism to the nails when they were removed. 

Next make two piles of books on the table and lay 
the sheet of paper across from one to another to form 
a little bridge. Stretch the paper tight and put more 
books on the edges to keep it in place. Then scatter 
some of the iron filings on the paper, and then hold 
the magnet under and touching the paper. Move it 
about in that position and the iron filings will follow 



the magnet-clock: 79 

the unseen magnet in the most curious manner possi- 
ble. 

A novel use was recently made of this experi- 
ment. The figures of a clock were painted on a tam- 
bourine so that it looked like a clock dial. The tam- 
bourine was then used for the cover of a neat box. On 
the upper side was an imitation beetle or spider, made 
of iron, that travelled round the clock face and thus in- 
dicated the time of day. There was no machinery 
visible and it seemed marvellous that the beetle thus 
moved round and round the clock dial. It was all 
simple enough when you were told that under the 
tambourine was a real clock with a magnet for 
an hour hand, and, as the magnet moved round 
and round, the armature-beetle crept after it. 

In like manner you can make the iron filings assume 
the most fantastic figures by moving the magnet about 
under the paper. You easily see what this experiment 
shows. The magnetic attraction passes through the 
paper. It is not a non-conductor. You can also try 
silk, linen, or other materials, and prove that none of 
them are non-conductors. The paper is really a con- 
ductor, that is, the magnetism passes through it, but it 
cannot conduct the magnetism to a distance as we saw 
copper conduct electricity. If a thick board is used in 
place of the paper it may appear to be a non-conductor. 



80 FIRST STEPS IN ELECTRICITY. 

Eepeat the experiment with the armature and magnet 
alone and you recall the fact that the power of attrac- 
tion extends only a little way from the magnet. The 
thick board does not cut off the magnetism from the 
iron filings, but simply keeps them beyond the reach 
of the attraction. The little space about the poles of 
the magnet where the magnetic attraction is felt is 
called the magnetic field. The board is merely thicker 
than the field is wide. 

Try the paper bridge and the iron filings again. 
Hold the magnet under the paper and then give the 
paper a> little snap or jar with the finger to make the 
filings dance about, and they will form curious groups 
around the spot over the ends of the magnet. This 
grouping of the filings shows how the magnetic field 
extends invisibly about the poles of the magnet. There 
is in this experiment another matter we might consider, 
but will leave it for the present while we look at some- 
thing else. 

Next use the paper bridge to test other things to see 
if they are attracted by the magnet. Try copper or 
brass filings, feathers, sand of any kind, or other light 
objects. Try larger things directly with the magnet, 
and make a list of the things that are attracted. You 
will find it a very small list. Try metals and alloys of 
metals. If the alloys contain iron they will be attracted 



MAGNETS IN MILLS. 81 

though there may also be other metals mixed with it. 
A very pretty test experiment is to try the magnet on 
pins. If they are attracted they are made of iron wire 
that has been whitened or silvered. If they are not 
attracted they are of brass. A curious use for magnets 
has been found in our great flour mills and elevators. 
Groups or "gangs" of magnets are placed in the 
spouts that are used to convey wheat or corn to the 
stones or bins in the mills and elevators. The corn 
and wheat sweep past untouched. A rusty nail, or bit 
of iron wire from a wire-binder in the wheat field, a 
speck of iron from the harvester passing through the 
spout is caught by the magnets and thus kept out of 
the mill-stones where it might do great harm to the 
stones or be turned to dust and mixed with our break- 
fast rolls. 

Get a large straight steel knitting-needle and hold- 
ing it by one hand draw it twenty times across the 
poles of the magnet. Touch the iron filings with the 
needle and you see that it too is a magnet. Try the 
armature on the magnet to see if it has lost any of its 
magnetism. It is as strong as ever and you see at once 
another curious thing. A permanent magnet may give 
magnetism to a piece of steel without apparent loss to 
itself, and the steel will become a new permanent mag* 
net. We have now a straight or bar magnet. Eoll the 
6 



82 FIRST STEPS IN ELECTRICITY. 

bar magnet in the iron filings and they will gather at 
each end in curious bunches,, and showing exactly 
how the invisible magnetic field covers the two poles. 
Wipe off the iron filings and let us try something else. 
Get a thread, and tying it round the middle of the 
magnetized needle, hang it up so that it will swing 
freely in any direction. When it is resting, quietly sup- 
ported by the thread in the middle, bring the horse- 
shoe magnet (without the armature) near it, and the 
needle being attracted will swing round towards it. 
Xow carry out the experiment very carefully in this 
way: bring one arm of the magnet near one end of the 
needle, and the needle will be either attracted or re- 
pelled. It will be one or the other very plainly. Look 
at the magnet, and on one arm you will find a mark. 
This is to indicate the positive or north pole (or end) of 
the magnet. The other end is called the south or neg- 
ative pole. Recalling your electrical experiments we re- 
member that positive attracts negative and repels posi- 
tive, and that negative electricity behaves in relatively 
the same way. We reduced this to a law by saying, un- 
like attracts, like repels. Our suspended magnet obeys 
the same law. It has a positive and a negative pole, 
and by experiment we can discover which end is posi- 
tive, and which is negative. If the positive pole of the 
magnet repels one end of the needle, that end must be 



MAGNETIC INDUCTION. 83 

positive and the other end negative, and the opposite 
holds true if tried with the other pole of the magnet. 
This gives us the law of magnets, like poles repel, 
unlike poles attract. 

Let us return to the magnet. Put on the armature 
and hold it near a tack. It clings to the armature, and 
with a little practice you can cause the suspended tack 
to pick up another, and that another, till you have a 
string of half a dozen hanging by the magnet. Here 
is a most singular thing, because you see that the last 
or lowest tack is far away from the small magnetic field 
of the magnet itself. Try to attract the tack when 
resting alone at the same distance it is now and no 
effect will be seen. It is too far away to be attracted 
and yet there it hangs. This comes from the fact 
that each tack in the line is for the time a little tem- 
porary magnet. The first one becomes a magnet by 
induction, and that by induction controls the next, 
and so on. Thus there is magnetic induction as well 
as electrical induction. Eefer again to your note-book 
to understand this clearly. This induction explains 
also the groupings of the iron filings on the paper 
and on the ends of the bar magnet. Each little parti- 
cle of iron became by induction a magnet. 

In some school cabinets can be found a small mag- 
netized needle that can be balanced on a little standard. 



84 FIKST STEPS IN ELECTRICITY. 

This apparatus is called a dipping needle, and, if. you 
had one, experiment would prove that it has, like the 
suspended needle, a north and a south pole. 

Observe now that while such a needle is at rest it at 
all times points in one particular direction. Why it 
should behave in this way we shall discover by later ex- 
periments, and we must be content now to know that 
this direction is north or toward the magnetic pole of 
the earth. You perhaps recognize this needle as the 
basis of the mariner's compass, the oldest and perhaps 
the most important scientific tool ever made, and the 
only practical application made of magnetism until 
modern times. 

By its use ships can be guided across the sea and 
without it navigation would be almost impossible. It 
is plain we have opened the door to a most fascinating 
and delightful field of experiment. You could go on 
for a long time studying these laws of magnetism, but 
already we are in sight of our old road. The cross-cut 
path brings us back to electricity far in advance of the 
place where we left it. Keep your notes on mag- 
netism. You will need them for reference in future 
work. 



CHAPTEE VI. 

CURRENT ELECTRICITY. THE ELECTRO-MAGNET. ELEC- 
TRO-MAGNETISM. 

Get a copper two-cent piece and at the tinman's buy 
a bit of sheet-roofing zinc, about two inches square. 
Get also a few yards of fine insulated copper wire. 
This is wire bound with fine threads of silk or other 
material. You see what is meant by insulated ivire. 
It is a wire conductor protected everywhere by a non- 
conductor so that when electricity is sent through the 
copper, it will not escape to your hands and thus be 
lost. Punch a hole in the zinc, and then scraping some 
of the insulation from the end of the wire, tie the bare 
wire to the zinc through the hole. Cut it off about 
two feet long and remove an inch of the insulation 
from the other end. Prepare another piece of wire in 
the same way and twist one of the bare ends round the 
copper coin. Then, holding the two metals by the 
wires, drop them into a cup of strong vinegar, taking 
pains to see that the zinc and copper are well covered 
and that they do not touch each other. The wires 

85 



86 FIRST STEPS IN ELECTRICITY. 

must hang oyer the edge of the cup and not touch 
each other. 

Nothing appears to happen. The two metals seem 
to rest quietly in the vinegar without producing any 
effect whatever. There is really a chemical change 
going on in the cup. The acid is attacking the two 
metals, the zinc slowly and the copper very slowly. 
In time part of the zinc will be quite eaten away. 
Touch the bare copper of one of the wires to your 
tongue. There is nothing. Try the other — no effect. 
Now put the ends of both wires on your tongue at the 
same time. There is a faint, acrid, biting taste on the 
tongue as long as the two wires rest there. This effect 
is certainly quite different from anything we have ob- 
served before. Very little can be done w T ith this ap- 
paratus except to give this peculiar taste in the mouth. 
By using better apparatus you will discover that we 
are once more on the old path we travelled before we 
turned aside to look at magnetism. 

Our work now requires more complicated apparatus, 
and you should get, if possible, what is called a small 
galvanic battery. The apparatus consists of a glass 
bottle with a brass stopper, and suspended from the 
stopper are two pieces of carbon and a piece of zinc. 
The zinc is fastened to a rod so that it can be raised and 
lowered at will, a set screw being used to hold the rod 



EXPERIMENTS WITH A BATTERY. 87 

in place In the bottle is placed a mixture of sulphur- 
ic acid and a solution of bi-chromate of potash. 

Such an apparatus is called a battery, and is made 
ready for our work by loosening the set-screw and 
letting the zinc drop into the liquid, On the top of 
the bottle are two pieces of brass called binding posts. 
Use the insulated copper wires again, and fasten the 
bared end of each piece to the binding posts by slip- 
ping the ends into the little holes and fastening them 
in place by the screws. 

Next, open the blade of your pocket knife that has 
the little file for the finger nail, and twist one end of 
the bared wire round the blade. Hold the other wire 
by the insulated part and touch the end to the file. 
As they meet there will be a tiny spark. Try the ex- 
periment in a dark room and drag the end .of the wire 
over the file and a little shower of sparks will fly from 
the file. Picture No. XII. shows how the experiment 
is done. 

It is plain that these sparks are electrical. They 
resemble the sparks from the electrical machine, except 
that they are more numerous and seem to come from 
the file and the wire in a continuous stream or current. 
You have again obtained electricity and without fric- 
tion or any apparent motion and without any exertion 



FIKST STEPS IN ELECTRICITY. 



on your part. This battery is clearly very different 
from the glass tube, the electrophorus and the electri- 
cal machine. You have seen that motion and friction 
or mechanical action can be used to produce electricity. 
Here we have chemical action. We can understand by 
imagination what takes place in the battery. Acids 




No. XII. 
corrode and dissolve metals. Now it has been learn- 
ed from a long series of experiments that acids dis- 
solve metals at different rates. For instance, vinegar 
is an acid and it attacks zinc slowly. It also attacks 
copper, but very slowly indeed. In your battery a 
stronger acid is used and zinc and carbon are exposed 



CURRENT ELECTRICITY. 89 

to it and are attacked or dissolved (eaten up), but the 
zinc faster than the carbon. 

Here are two chemical actions going on side by side 
at different speeds, and whenever this happens the elec- 
trical quiet is disturbed. Just as with friction the two 
electricities are pulled apart, so in the battery there is a 
pulling apart and there is a positive electricity and a 
negative electricity each trying to get away from each 
other, and each trying to find its opposite that they 
may rush together and restore the balance upset by 
the action of the acid on the metals. 

In the electrical machine you obtained a spark, and 
then another and another, and so on. It was a series 
of different electrical effects with little pauses between 
the sparks. In the Leyden-jar you saw a series of these 
sparks all joined together in one bright flash. When 
the zinc and copper were placed in the cup of vinegar 
electrical action began at once and then continued. 
You remember the peculiar taste on the tongue was 
continuous as long as the wires touched the tongue. 

In your last experiment it seemed as if the sparks were 
broken and came one after the other. It was really a 
continuous stream or current, the sparks appearing at 
the instant when the wire and the knife blade touched or 
were pulled apart. Thus electricity from a battery or 
from a chemical source is called current electricity, to 



90 FIRST STEPS IN ELECTRICITY. 

distinguish it from the static electricity you obtained 
by friction. While the two metals rest in the acid 
there is electrical action, but it is invisible and not of 
much use. By fastening a conductor to each of the 
metals we make a path for the two electricities to travel 
up from the metals and acid. When you bring the 
bared ends of the two wires together, positive and 
negative rush across through the air in a tiny spark, 
giving both heat and light. Then, so long as the 
wires touch, the positive and negative flow silently and 
invisibly in a current or stream through the two con- 
ductors. Pull the wires apart and we see the flash as 
they try to leap across at the instant the wires part. 
Every time the ends of the wires are brought together 
or pulled apart we catch a glimpse of the current that 
is always flowing through the wires when they are 
joined together. Lift the zinc out of the acid and all 
action stops. There is now only the carbon in the acid 
bath and no electrical effects appear. 

Put the zinc back and you have two materials dissolv- 
ing at different speeds, and electricity flows like an in- 
visible rivulet between them along the joined wires. 
Even when the wires are not joined there will be a cur- 
rent if the ends of the two wires touch another con- 
ductor (like a gas lamp), for the current will flow away 
into the earth. Each polarity will seek its opposite by 



CURRENT ELECTRICITY. 91 

our old law — unlike attracts — and the electrical action 
will go on growing fainter and fainter till the acid is too 
weak to affect the metals, or till the zinc is so injured 
that it will no longer dissolve, or till it completely dis- 
appears. For this reason you will find it a good plan 
always to lift the zinc out of the acid when you are not 
using the battery, and thus prevent the battery from 
wearing out. 

You might go on and perform many interesting exper- 
iments showing the character and behavior of this cur- 
rent electricity, and its effects upon different materials. 
Our aim is to see how electricity can be used in work, 
in business and social life, and we must omit many 
things that are both curious and interesting and take 
up experiments that may help us to understand the 
uses of electricity. It is sufficient now to observe that 
current electricity is both positive and negative, and 
that it behaves according to the same laws of attrac- 
tion and repulsion and manifests all the effects of in- 
duction that you observed in your previous experiments. 
Take the wires off the knife blade and prepare for 
another experiment. Now the two wires are separated 
and the current ceases to act. Next, fasten the two 
wires together by twisting the ends firmly. Now the 
conductors touch and the current is silently flowing 
through both and we have what is called a closed circuit. 



92 FIRST STEPS IN ELECTRICITY. 

When the wires are separated, even for a very small 
space, the circuit is said to be open ; it is an open cir- 
cuit. When the circuit is closed the current flows 
till the zinc is lifted out of the acid. When the zinc 
is again lowered into the acid the current flows again. 
So there are two ways of opening the circuit : first, by 
breaking the wire, and, second, by raising the zinc and 
stopping the chemical action in the battery. When 
the battery is in order and the circuit closed, the cur- 
rent will flow for many hours or till the zinc is de- 
stroyed or the acid becomes so weak it will not work. 
Fasten the two wires together to close the circuit 
and get the dipping needle. Lift the zinc in the bat- 
tery, and then hold a portion of the wire straight and 
parallel to the needle and just above it. While the 
wire is in this position have the zinc lowered into the 
acid, and at once the needle behaves in a most singular 
manner. It forgets to turn to the north and swings 
round and at a right angle with the wire. Unfasten 
the wires and bend the ends into hooks and then, while 
one person holds the wire over the needle, let another 
close and open the circuit by means of the hooks. 
Each time the circuit is closed the needle will stand 
across the wire. It is plain that the current in the 
wire has some mysterious influence over the needle, 
and you can perform a number of interesting experi- 



THE NEEDLE IN A CURRENT. 



93 



ments by holding the wire under as well as over the 
magnet and in different parts of the circuit. Picture 
Xo. XIII. shows the way in which this experiment 
should be performed. 

This experiment, simple as it is, shows us one of the 




No. XIII. 
great laws in electrical science. Study the experiment 
carefully and see what it means. The dipping needle 
is a magnet and, being free to move, it turns to the north 
or towards the magnetic pole. When the insulated 
conductor is held over it, the current in the conductor 
has the power of turning the needle till it stands di- 
rectly across the conductor. It cannot be the wire, 
because only when the circuit is closed and the current 
flows does it behave in this singular manner. As this 
always happens, w 7 e say it is a law of freely suspended 



94 FIKST STEPS IN ELECTRICITY. 

magnets that they stand always at right angles or 
across the path of any current of electricity passing 
near them. As the conductor is insulated this behavior 
of the needle is caused by induction, for you will ob- 
serve the needle does not touch the wire and is not 
brought into contact with the conductor and cannot 
be electrified. 

Two curious facts suggest themselves by this experi- 
ment. When the dipping needle is free to move as it 
will, it always points to the north. If it turns across 
the path of an electrical current, may there not be at 
all times currents of electricity flowing from west to 
east round the earth. We cannot think of any other 
reason why the needle points north, and, though we 
cannot see or feel these earth currents travelling round 
our planet, every mariner's compass seems to plainly 
show that such currents do always travel round the 
world. 

Another and more useful fact is indicated by your 
experiment. If the needle turns in this way across 
the path of an electrical current, may it not be 
used to indicate the presence of a current. This is 
plainly what happened, for only when the circuit was 
closed did the needle move, and by watching the needle 
you could tell precisely when the current flowed even 



THE GALVANOMETER. , 95 

though you had no other means of knowing it was in 
the wire. From this you see it was not difficult to 
make a machine for detecting the presence of electric- 
ity. This little experiment is the basis of a remark- 
able apparatus called a galvanometer, and used to detect 
and measure a current of electricity in any conductor. 
The galvanometer has a swinging needle that marks 
the presence of the most feeble and delicate currents,, 
and proves that they are moving when they are so 
feeble that w r e have no other means of detecting their 
presence. 

This swinging magnetic needle was at one time 
used in telegraphing, and is still used in long ca- 
bles under the sea, its swing to and fro as the cir- 
cuit is opened and closed indicating the letters of 
the words in a cable message. We might spend a 
long time in studying the galvanometer and learn 
much that is both curious and interesting. It is best, 
however, to turn to another experiment showing a 
still closer connection between electricity and mag- 
netism. 

Get a common iron key and wind the insulated part 
of one of the wires round and round the key in a spiral 
from the handle to the wards. Leave the end of the 
wire loose to form a hook as before and to be used in 
closing and opening the circuit. Leave the circuit 



96 FIRST STEPS IN ELECTRICITY. 

open and get a tack, a small hair-pin/ or other small 
iron object. Touch it with the key, holding it by 
the handle. There is no effect. Now close the circuit 
and try the key again and we discover perhaps the 
most remarkable thing in this science. The key is a 
magnet. Open the circuit and the key ceases to be a 
magnet. Close it again and it once more attracts 
small pieces of iron, and they cling to it precisely as to 
our horseshoe magnet. Observe the conditions of our 
experiment. "We have a piece of soft iron (the key), 
and we have twisted about it an insulated wire convey- 
ing a current of electricity. The silk prevents the 
electricity from escaping to the key or from leaping 
across from spiral to spiral along the key, and it must 
travel round and round it. The result is extraordi- 
nary. The soft iron key is a magnet as long as the 
current flows, and ceases to be a magnet the instant the 
circuit is broken. Picture No. XIV. shows just how 
the whole affair works. 

We have here a current of electricity flowing round an 
iron bar and insulated from it. The effect is therefore 
caused by induction. It is an induced magnet and as 
it is given this property by electricity it is called an 
electro-magnet. We have used a small battery, a little 
insulated wire and an iron key, and yet with these sim- 



THE ELECTRO-MAGNET. 



97 



pie things we have made the most remarkable and per- 
haps the most useful tool ever invented. 

The electro-magnet is now as common as the plough, 
the sewing-machine, the loom, or printing-press, and 
like these great tools it has entered into our daily life 




No. XIV. 



and business and marks one of the great steps of 
human progress. As electricity can in this simple 
manner be used to make an electro-magnet, the mag- 
netism displayed by the soft iron while it is affected by 
the current has naturally received the name of electro- 
7 



98 FIRST STEPS IN ELECTRICITY. 

magnetism. This makes the last and most valuable of 
the magnets, and we have now the natural magnets or 
loadstones, the temporary magnets, as when a piece of 
soft iron is touched to a magnet, the permanent mag- 
nets, and the electro-magnets. We have the perma- 
nent magnetism of the horseshoe magnets and the elec- 
tro-magnetism of the electro-magnets. The dipping 
needle may be an electro-magnet; the currents of elec- 
tricity travelling round the earth from west to east cre- 
ate electro-magnetism in it. Our earth itself is a great 
magnet. 

It is not difficult to go a step farther in imagina- 
tion and trace electricity and magnetism to the sun 
and even to the most distant star. There are, the as- 
tronomers tell us, electrical disturbances in the sun, and 
when such electrical storms rage in the sun 90,000,000 
miles away, every little electro-magnet in our telegraph 
offices is affected by some strange magnetic sympathy 
across the interstellar spaces. May not all action, me- 
chanical or chemical, whether it be the turning of a 
little crank or the swift swing of a giant star create 
electricity and turn whole worlds into electro-magnets. 

The acid in a cup stirs a current in two bits of metal. 
May not the sea and land or the materials of a sun be 
vast batteries producing currents that reach across the 
world and the universe. There is no longer anything 
special or peculiar to our little world. Electricity and 



GALYAXISM. 99 

magnetism are intimately related, they may be even 
different manifestations of the same thing, and they 
are universal. The laws we have learned from your 
little experiments operate here and in the most distant 
star. 

In 1790 Galyani made his first famous experiments 
in electricity and gave his name to this particular form 
of electricity we have examined and it was at first 
called Galvanism. In 1792 Volta, of Pavia, carried 
Galvani's experiments still further and his name also 
became associated with the science, as electricity from a 
battery is sometimes called Voltaic electricity. Oer- 
sted and Ampere carried out researches in electro-mag- 
netism and made its laws known, and Faraday contrib- 
uted many great and important experiments in this 
science. Had we time we could well afford to spend a 
year's study in this one branch of electricity. As it is, 
all we can do is to remember what we have learned in 
order to apply our knowledge to the understanding of 
the practical uses of electricity in w T ork and business. 



CHAPTER VIL 

THE LAST STEPS. ELECTRIC SIGNALS. THE TELE- 
GRAPH. THE TELEPHONE, THE ELECTRIC LIGHT. 
THE UNITY OF NATURE. 

We have now observed some of the more simple 

manifestations of electricity. You have demonstrated 

by experiment the few grand laws that govern these 

manifestations, and you have shown how electricity 

may produce magnetism. One more step upward and 

we shall reach high ground, where we can look back 

along our path and look abroad over the whole 

vast field of magnetic and electric invention. When 

we have made this last step in electricity we shall be 

able to understand something of the general principles 

governing all the marvellous machines and appliances 

that have produced such wonderful changes within the 

p^st few years. Our first steps may seem only a few 

easy paces on a long and intricate road, yet it is one of 

the wonders of nature that, when we come earnestly to 

study her laws, we find these laws are few in number 

and as complete in operation as they are simple in. de« 

sign. 

100 



THE INDUCTION COIL. 101 

111 the school cabinets can be found a small apparatus 
resembling a barrel or cylinder. It consists of two coils 
of insulated copper wire, one formed of a long piece of 
line wire and the other made of a shorter piece of much 
larger wire. The shorter coil is placed inside the 
longer coil and each is carefully insulated from the 
other. The inside or short coil is called the primary 
coil The larger outside coil is called the secondary 
coil While one is much larger than the other they 
are both wound in spirals, and being one inside the 
other the two wires are parallel through all their 
windings. The primary coil can be connected, by 
means of short wires, with the battery, and a current of 
electricity will then travel through the primary coil 
inside the secondary coil. While the current thus 
flows through the primary coil nothing appears to 
happen. Open the circuit (by means of hooks as in 
your experiment with the current and dipping needle), 
and at the instant the circuit is opened there will be a 
throb of electricity in the secondary coil. It is like a 
beat or pulse and lasts only for an instant. On closing 
the circuit the same momentary flash of electricity will 
stir in the secondary coil. If you can open and close 
the circuit very quickly, there will be in the secondary 
coil a series of these electrical beats following each 
other just as fast as you make and break the circuit. 



102 FIRST STEPS IN ELECTRICITY. 

By using the discharger you made for the Leyden-jar 
you can obtain brilliant sparks from the two binding 
posts on top of the apparatus. This secondary current, 
produced at every make and break in the primary cur- 
rent, is said to be induced. The apparatus works by 
induction and is called an induction coil. The second- 
ary current is also called an alternating current because 
its direction or polarity (positive or negative) is 
changed alternately at every opening and closing of 
the primary circuit. 

In some induction coils the primary is enclosed in the 
secondary and cannot be taken out. If it could be 
taken out and put back at will, you might perform 
another experiment. Suppose you could do this and 
that the primary coil was connected with the battery 
(closed circuit) and the current passed through it. 
Then on putting it inside the secondary coil there 
would be the same short pulse or beat of electricity in 
the secondary coil. There would be the same effect on 
taking it out. The experiment would show that the 
mere movement of a coil carrying a current will induce 
a secondary current when it is put in or taken out of 
the secondary coil, and without making or breaking 
the primary circuit. There are thus two ways of pro- ' 
ducing the secondary current, the first, however, be- 
ing the most simple and easy. 



ELECTRICITY FROM MAGNETISM. 103 

You have already seen by your experiments with the 
electro-magnet that electricity will produce magnetism. 
By the aid of an induction coil it has been learned that 
magnetism may produce electricity. If a bar magnet 
be pushed into a secondary coil (the primary coil being- 
taken out), there will be a pulse of electricity in the 
secondary coil at the instant it is put inside the coil. 
The same thing will take place when it is taken out, 
the direction of the secondary current changing each 
time the magnet is put in or taken out. Another 
curious fact has been learned. If a piece of soft iron 
or a bundle of iron wires is put in a secondary coil and 
then a permanent magnet is brought near the soft iron 
(in the coil) it will become a magnet by induction. 
(This you have already proved.) Then, if the magnet 
is merely moved forward or backward before the iron a 
current of electricity will appear in the secondary coil. 
We could go one step farther and put the permanent 
magnet inside the coil, and then holding the armature 
in the hand move it backward and forward in the field 
of the magnet and produce a secondary current of elec- 
tricity in the coil. 

The same thing would happen if an electro-magnet 
were placed inside the secondary coil. In the induc- 
tion coils used in schools there is, inside the primary 
coil, a bundle of soft iron wires, and at one end of the 



104 FIRST STEPS IN ELECTRICITY. 

bundle is an armature supported by a spring. If you 
connect the primary coil with your battery, the bundle 
of wires becomes an electro-magnet. The armature 
will be then attracted towards the wires and touch 
them. At once the spring would tend to pull it away, 
and in doing so would, by means of a shunt or short 
loop wire, open the circuit. Attraction would cease, 
but the recoil or backward movement of the spring 
would throw it into place again, close the circuit and 
bring it in the magnetic field only to be attracted 
again. In this manner the armature would rapidly 
beat backward and forward alternately making and 
breaking the circuit. This rapid opening and closing 
of the circuit would produce a rapid stream of alter- 
nating positive and negative beats that would form a 
powerful electric-current. Connect the two binding 
posts on top of the coil and this secondary current can 
be used for experiments. Try the two wires and file 
used in your experiment with the electrical battery 
and a brilliant shower of sparks will be obtained. Use 
care with this apparatus as the secondary current may 
give unpleasant shocks if allowed to pass through the 
hands. 

Electricity obtained by induction from any form of 
magnet is called magneto-electricity , and any apparatus 
using such electricity is called a magneto-electric appa- 



MAGNETO-ELECTRICITY. 105 

ratus. This method of obtaining electricity is now 
the most important and the cheapest, and as a result is 
the most common wherever large and powerful cur- 
rents are used. 

Let us take one more step. Suppose we have two 
magnets, one a large permanent magnet and the other 
a small electro-magnet. By using these together it 
would be possible to obtain currents of electricity 
without the use of a battery. Not from the magnets 
alone. In nature there is no such thing as a gift. 
There must be something paid for something re- 
ceived. To these magnets we must add motion or 
movement of some kind. From what we have learned 
it is easy to imagine that if the poles of the electro- 
magnet are brought near the poles of the permanent 
magnet there will be a throb of electricity in the wire 
wound round the electro-magnet. This flash of elec- 
tricity would appear in the wires just as the electro- 
magnet entered the magnetic field. In like manner 
there would be another pulse or beat in the wire, when 
the electro-magnet is taken out of the field. There is 
motion or movement in each case and we learn that 
motion will produce electricity. It would not be diffi- 
cult to mount the electro-magnet on a shaft, and by 
means of a crank to cause its poles to pass in turn 
through the. magnetic field. Each time its poles en« 



106 FIRST STEPS IN ELECTRICITY. 

tered and left the field there would be an induced cur- 
rent in the wires of the electro-magnet. If the crank 
was then turned very fast, the beats or throbs of elec- 
tricity would follow quickly in a stream. By means of 
springs resting on the revolving electro-magnet we 
could conduct the current to a wire and thus lead it 
anywhere we wished. 

It is not surprising that having learned this much 
men soon took one more step, the last and most impor- 
tant of all. In place of the permanent magnet as a 
source of magnetism an electro-magnet was used, and 
to charge it a part of the current from the moving 
magnet was taken through its coil, and thus magnetism 
was obtained in large quantities and used to induce 
still larger quantities of electricity. This brings us to 
a point that seems to form a new starting-place in this 
science. A water-wheel or steam-engine could be har- 
nessed to such a magneto-electric machine and its 
force or power be used to obtain electricity. Such a 
machine is called a dynamo-electric machine or simply a 
dynamo. It means literally — force-elect ric-macliine or 
power machine. We cannot use a dynamo in your ex- 
periments as they are costly and demand great force to 
move them. We can, however, see presently what 
can be done with the great streams of electricity that 
flow from a dynamo. 



A WIDE OUTLOOK. 107 

These last steps taken in imagination bring us, as it 
were, to the top of a hill where we can rest and look 
about. Before us are all the strange new tools and 
apparatus used in electricity. At first glance they 
seem mysterious and complicated, yet all are founded 
on the few simple laws shown to us by your experi- 
ments. The road stretches on and upward along many 
a steep and difficult path 'til it is lost in the mist that 
seems to hide the unknown and undiscovered. While 
we may not all of us go any farther along this road 
we may be sure that those who do so will find the same 
laws governing all the manifestations of electricity 
in both nature and art. You should go on. It is to 
be hoped you will take with other guides more steps 
in the study of nature, and advance to more skill in ex- 
perimenting, more knowledge, and a wider outlook over 
this great field of science. 

However, even these few steps have brought us to a 
point where we can understand the general principles 
that underlie all electrical work. Suppose we look 
about a little and try to see how the laws demonstrated 
by your experiments are used in the arts, in manufact- 
ures and business. We call at a friend's house and look 
for the big brass knocker or the handle of the door 
bell. They have disappeared and instead of lifting the 
heavy knocker or pulling, the handle. we gently touch 



108 FIRST STEPS IN ELECTRICITY. 

a button with one finger. The merest touch, and yet 
in a moment the maid opens the door. She must have 
been informed in some way that we were at the door. 
We ask how it was done. It is perfectly proper to do 
so. Always ask questions. Never hesitate to inquire 
about any matter you do not understand. Better be 
inquisitive than ignorant. 

Our friend shows us the whole thing. Simple 
enough — a little battery, some wires, an electro-mag- 
net, and a bell. The whole affair is arranged in this 
way. In some closet is a battery. From this battery 
extend along the walls or behind the plastering two 
wires. They reach to the front door, then to the 
kitchen and then to the battery and form an insu- 
lated circuit for the battery current. At the door the 
wire is cut and forms an open circuit precisely as in 
your experiments. The two ends are close together 
and when we touched the little button at the door we 
merely pushed them together and closed the circuit. 
In the kitchen the wires are joined to the coil of a 
little electro-magnet. For an armature this electro- 
magnet has a bar of soft iron supported on a spring, 
and carrying a rod having a little hammer that hangs 
near a brass bell. When the circuit is open the electro- 
magnet is quiet and inactive and the spring keeps the 
armature away from its poles. When we closed the 



ELECTRIC BELLS. , 109 

circuit at the door the magnet attracted the armature 
and its hammer struck the bell, and the sound notified 
the maid that we wished to enter the house. When 
we released the push-button the circuit opened, the 
magnet was demagnetized and the armature was pulled 
back into its old place ready to strike again the next 
time the circuit is closed. 

In this simple apparatus, w T hich you might rig up 
for yourself at home for a dollar or two, we have the 
general principle on which all call bells, alarms, indica- 
tors, fire and burglar alarms of every kind are made. 
There are, of course, a great many modifications, 
many different methods of using these principles, and 
in some appliances of this kind there are many com- 
plicated and apparently perplexing details. Yet, un- 
der all changes, through ail the many curious details, 
there are these two ideas, a battery and circuit and 
an electro-magnet. There are also many kinds of 
bells used in such electric alarms. There are tiny 
chattering bells that whir and tinkle in fretful repeti- 
tions. There are big bells that strike loud strokes, 
one, two, three, or more times, each stroke serving for 
a signal. For instance one stroke may mean the 
maid is wanted, two strokes a fire is wanted upstairs, 
or three strokes tell that breakfast is ready. The bells 
may be hung high in church steeples and suddenly in 



110 FIRST STEPS IK ELECTRICITY. 

the quiet night, when all the town is asleep, every bell 
may clang out curious numbered strokes that tell of a 
fire in some district. The booming sounds come over 
the house tops in succession from far and near bells, 
and make a musical clamor on the air. Yet, really, 
every bell was struck at the same instant by one man, 
who with a touch of the finger clangs twenty church 
bells, miles apart over the city. 

We go to a hotel and see in the office a large dial 
having many numbers, each covered by a little shield 
or mask. We hear a bell ring and see one of the 
shields fall and display a number. Here is both a 
signal by sound, and also a visible signal or number to 
indicate in which room of the house the circuit was 
closed. We call at a factory and see on the ceiling 
little discs of metal placed at intervals between two 
wires that stretch along the ceiling. We ask what 
that means and the proprietor tells us that, if a blaze 
should start up from the machinery of the factory 
and threaten to burn the building down, one of those 
discs on the ceiling would melt and the fire bells would 
ring at the nearest engine house. The ordinary heat 
of the room would not affect the discs. A lighted 
match held close to one of them would melt it, close 
or open the circuit through the wires, and sound the 
fire bells. " 



PRACTICAL ELECTRICITY. HI 

We visit a farm and are shown an incubator or ma- 
chine for hatching eggs by artificial heat. Now in 
such an apparatus it is very important that the tem- 
perature in which the eggs are kept should be the 
same at all times. There is a thermometer inside to 
show the temperature. Certainly it is a most curious 
thermometer for, if the mercury rises too high the 
dampers of the fire are turned or the wicks are turned 
down in the oil stove. Soon the mercury falls again 
and then by some mysterious apparatus the wicks are 
turned up and the stove gives out its heat again. It's 
not so mysterious as it appears. We may be sure that 
somewhere near is a battery or conductor forming a 
circuit and an electro-magnet. We call on some 
friend who lives in a house having the very latest im- 
provements and find in every room a thermometer 
that closes the dampers in the furnace the moment the 
rooms become too warm. 

Perhaps we go down Broadway in New York at noon 
and see hundreds of people looking at a black ball on a 
pole- at the top of a large building, on the corner of 
Dey Street. Suddenly the ball drops to the foot of 
the pole, and all the people look at their watches to 
see if they agree with the government clock at Wash- 
ington. W^e enter a business office near by and find. a 
curious machine covered by a glass bell. The machine 



112 FIKST STEPS IN ELECTEICITY. 

moves by fits and starts, and from a slit in the side of 
the case supporting the glass cover slides out a ribbon 
of paper having curious marks and letters printed on 
it. Dignified old gentlemen read the paper ribbon 
with becoming gravity, as if in search of valuable in- 
formation. It seems very odd to see an elderly gentle- 
man watch such a fretful little machine. When we 
learn that a battery, a circuit, and some electro-magnets 
are telling him the news of the market we begin to see 
how your little experiments explain complicated inven- 
tions of the greatest value to business men all over the 
world. 

We go to a bank near by and find singular doors and 
windows and curious door-mats. The bank president 
informs us that, if at night when the bank is closed, 
any one should open a door or window, or even tread 
on that innocent mat, an electric circuit would be 
opened, an armature clinging to its electro-magnet 
would be released and fall, striking a bell and showing 
a number in the nearest police station and the officers 
would quickly be on hand to see what was the matter. 
The robber might know all this and cut the wires. 
This would be a pretty mistake, for cutting the wire 
would be opening the circuit and the bell would clang 
and the police appear. 

An engineer of the express is leaning out his. cab win- 



ELECTRICITY AND RAILROADS. H3 

dow looking ahead for lights while his engine rushes 
along through the darkness. His life, the lives of all 
the people in the sleepers behind him depend on these 
lights along the way. He sees a white light ahead. 
All right, and he lets the throttle open a little wider. 
As the engine sweeps past, the white light turns to 
red. There is a curious click on the track hardly 
noticed in the roar of the train. Half a mile ahead a 
bell is ringing loudly at a lonely crossing in the w T oods. 
A belated milkman hears the bell and w T aits till the 
approaching train flies past and the crossing is safe. 
As the train approaches a town the sleepy passengers 
in the waiting-room hear a chattering bell and pick up 
their bags and wraps, glad to know the train is coming. 
The train moves on and suddenly the engineer sees a 
red light ahead. He shuts off steam, puts on the air 
brake, and with a jar the train stops. A train man 
goes ahead to the red light. Nothing to be seen. 
He goes on still further and finds a train stopped on 
the road. Hot box. K~o thoroughfare for the train 
behind till things are cooled off and the train in front 
goes on. The moment it is a mile away the red light 
changes to white. The line is clear. Go ahead. 

In all these instances and in many more equally 
curious and interesting you can trace your little exper- 
iment with the battery, the wires, and the iron key. 
8 



114 FffiST STEPS IjST ELECTRICITY. 

In each of these widely different applications of elec- 
tricity there is a battery, an electric circuit through 
some conductor, an electro-magnet whose armature 
moves forward or backward as the circuit is opened or 
closed. The forward wheel of the truck of the locomo- 
tive pushes down a lever that projects above the head 
of the rail. The circuit is closed, the red lamp dis- 
played, and the bells ring at the crossing and the sta- 
tion. The red lamp remains visible behind the train 
to warn any following train till the engine in front is 
a mile away, and then the wheel pushes down another 
lever, opens the circuit again and the armature of the 
electro-magnet by the lamp lets the red target fall and 
the lamp burns white again. It is the same in every 
messenger-call, burglar, or fire alarm, annunciator, 
time-ball, electric clock, electric heat regulator, elec- 
tric recorder, "ticker, 5 * railroad target, or other warn- 
ing bell or call of any kind. Through every complica- 
tion of machinery, under all the complex details there 
lies the law that at the opening of an electric circuit 
there is magnetism in a piece of soft iron round which 
the wire is wound. Your iron key and wire may seem 
a trifling bit of apparatus and yet they show the use of 
one of the most important tools ever invented. 

Eecalling your experiment you may wonder how 
such a small and weak attraction as the electro-magnet 



THE ELECTRO-MAGNET AT WORK. 115 

shows can produce such great results. Surely the tiny 
swing of the armature could not ring a church bell. 
This is a good question, but a few moments' thought 
will explain it. Take the time-ball. It is easy for a 
man to raise the ball on the pole and then to fasten 
the rope or other means of support to a spring, care- 
fully balanced so that the slightest touch will release 
it. The pendulum of the clock at Washington swings 
to and fro, and just at the right instant it strikes a 
little pin, opens the circuit in that city and the magnet 
at New York releases the spring and the ball falls. It 
is the same with the church bell. A heavy weight has 
been wound up and made fast to a carefully balanced 
spring or lever that will move at even the gentle 
touch of the electro-magnet. It is not the magnet 
or its armature that rings the bell, but the weight 
that in pulling swings the great hammer till the 
bell roars with sonorous clang. This may not be 
the precise way in which it is done, yet it explains the 
principle by which it is done. For instance, you 
remember that the burglar alarm operated on a circuit 
that was always closed, and that the opening of the 
circuit rings the alarm bell. A moment's thought 
shows how that is done. The circuit is closed and the 
electro-magnet holds the armature tight. When the 
circuit is broken the armature is released and by its 



116 FIRST STEPS m ELECTRICITY. 

weight or the pull of a spring it strikes the bell. It 
may operate in still another way. The release of the 
armature may set in motion clock-work already wound 
up and ready to start the instant the armature is free. 

The point is just this : — the opening or closing of an 
electric circuit causes the armature of a magnet to 
move. Its tiny spring gives us the power to control 
work at a distance. It makes no matter how compli- 
cated the mechanism, in every case the electro-magnet 
is the one tool that accomplishes all these wonders. 

The touch of a hand, the tread of a wheel, the pres- 
sure of a footstep, the rise of the mercury in a ther- 
mometer, the swing of a pendulum, any slight move- 
ment may open or close a circuit. In like manner the 
tiny play of an armature miles away may start or stop 
the most powerful machinery, be it controlled by a 
weight, or water wheel, or. steam-engine. So it comes 
that your experiment hints at great and splendid in- 
ventions whereby the gentle touch of a magnet may 
strike a church bell, move a railroad target, tend a 
furnace fire, set an engine in motion or steer a ship. 

We sometimes wonder at the telegraph and forget 
that this great science of signaling is its twin brother. 
All these uses of a battery and circuit and an electro- 
motor began with the birth of the telegraph about fifty 
years ago. Let us once more recall your experiments 



THE FIRST TELEGRAM. 117 

and see if they may not be a key to unlock the mystery 
of the telegraph. 

It is not difficult to imagine that, if a pen be 
fastened to an armature, its little swing to and fro, as 
the circuit is opened or closed, might be used to 
scratch marks on paper and these marks might stand 
for letters and words. On such a simple idea as this 
rests the great science of telegraphy. The first tele- 
graph used by Morse between Baltimore and AYashing- 
ton was no more than this : a battery, two wires, a key 
for opening and closing the circuit, an electro-magnet, 
and a little apparatus whereby the armature would 
make little dents on a ribbon of paper. Out of how 
small a matter have grown such marvellous things. It 
is no wonder that the first electro-magnet used to spell 
words at a distance scratched down these words : 
" What hath God* wrought ! " 

On page 132 is a reproduction of the very marks 
made by the first telegraph in sending this first tele- 
gram. They seem very rude and rough, yet they are 
full of interest as they show the finger marks of the first 
electro-magnet that wrote out a telegraphic message. 

From the simple telegraph invented by Morse has 
grown up in these fifty years a vast and complicated 
system of transmitting and receiving messages. Yet 
in all the alterations and improvements the laws de- 



118 FIRST STEPS IN ELECTRICITY. 

monstrated by your experiments hold good. In every 
phase of the science there is the battery, the circuit, 
and the electro-magnet. The first great step in ad- 
vance was the use of one wire instead of two. By in- 
serting the ends of a single wire in the ground, connec- 
tion is made with the great source of magnetism and 
electricity, the earth. The positive from the battery 
then flows through the line wire to the magnet and 
then seeks its negative in the earth. The positive of 
the earth in like manner flows up to the battery to 
meet its negative. The balance upset in the battery is 
restored and the polarities are satisfied precisely as if 
they met through a conductor forming a real circuit. 

When a current of electricity passes through a con- 
ductor it is weakened, and, if the wire is too long, it- 
may be so feeble that it cannot excite the electro-mag- 
net. This weakening is said to be caused by the resist- 
ance of the wire. To compensate for this loss of power, 
at the distant end of a long wire a second battery and cir- 
cuit is used and the electro-magnet is employed to open 
and close this second circuit. Such an arrangement is 
called a relay, and by the use of relays we are enabled to 
join circuit to circuit and thus send messages to great 
distances. 

Improvements were rapidly made in the original 
Morse system. One of the most simple was the use of a 



THE SOUNDER 119 

sounder, to enabxe the operator to read the message by 
sound instead of reading it from a recording apparatus. 
This sounder is merely a device for making an electro- 
magnet give out a loud click or beat each time it is 
moved, and its use reduced the receiving apparatus to 
the utmost simplicity. 

It was in time learned that, by variations in the char- 
acter of the current and the magnets, more than one 
message could be sent over one wire. For instance, 
one magnet might be sensitive to changes in the polar- 
ity of the current, while another might be sensitive to 
changes in the strength of the current only, and both 
would work over one line wire without interference. 
This idea in various forms led to duplex telegraphy. 
Other modifications led in time to the quadruplex sys- 
tem. More recently still, other changes that you could 
not understand without long study were introduced, 
and it is now possible to send many messages at one 
time over a single wire. Another great step was the 
invention of printing telegraphs that reproduced the 
actual words of the message sent over the wires. It 
was also discovered that if paper is wet with certain 
chemical solutions it is stained or discolored when an 
electric current is sent through it. This led to the 
chemical telegraphs, and by the use of certain machines 
it became possible to receive messages at a far more 



120 FIRST STEPS IN ELECTRICITY. 

rapid rate than they could be read on a sounder. Other 
improvements followed, and machines for transmitting 
messages were brought out. These transmitters, as 
they are called, made it possible to make and break 
the circuit many times a second. By combining the 
machine transmitters with the chemical recorders it is 
now perfectly easy to send many hundred words a min- 
ute over a single wire from Boston to New York. 

Our first steps have led us to the threshold of a great 
science wherein you might spend a long life and not 
reach the end. We cannot understand it all now. 
You should go on to further study at some future time. 
We can now only glance at it in passing to recognize that 
under all the bewildering variety and complexity are 
the few simple laws demonstrated by your experiments. 

In the telephone the electro-magnet is the basis of 
all the marvels of this wonderful invention. The 
sound of your voice is, in fact, a series of waves in 
the air. These beat on the armature of an electro- 
magnet and cause it to swing backward and forward in 
the field of the magnet. This slight movement causes 
delicate changes in the current in the coils of the mag- 
net. These changes, corresponding in number to the 
sound waves started by your voice, travel over the line 
and affect another magnet, and cause its magnetic 
attraction to come and go in waves, now strong, now 



THE TELEPHONE. 121 

weak. These variations in its magnetic field affect its 
armature, and it beats backward and forward and gives 
out to the air waves or pulsations that to the listener 
exactly resemble the sound of your voice. Again we 
see this wonderful tool called an electro-magnet per- 
forming an important part in the work of the world. 

AVhen a current flows along a large conductor noth- 
ing can be seen or felt to indicate ifcs presence. If 
there is a break in the wire and the broken ends are 
close together, the current may leap across through the 
air in an arching stream of fire. This fact has been 
known for many years, yet it was not until within a 
very few years that any practical use was made of it. 
There were two reasons for this. The gap between 
the wires must always be the same. If it is too small 
the current passes in silence or with only a small 
flame; if too large it cannot pass at all. The arching 
flame to be of any value as a lamp requires very large 
and costly batteries. These two things kept this elec- 
tric flame in the laboratory, and men thought of it only 
as a curious and expensive toy. 

With the invention of the dynamo large currents of 
electricity were made possible. Then, after various 
trials with clock-work and other devices to control the 
conductors, inventors fell back on that old tool the 
electro-magnet. By its aid it was possible to make the 



122 FIRST STEPS EST ELECTRICITY. 

current itself regulate the gap between the conductors, 
and then the splendid arc-lamp came to fill our streets 
and shops with its brilliant light. 

When a current travelling along a large conductor 
comes to a smaller conductor, it meets with resistance, 
and in its effort to overcome the resistance it heats the 
smaller wire. If the resistance is too strong the small 
wire may be heated white hot, perhaps be melted, or 
even completely burned up. This curious fact led 
to the invention of another form of electric light. 
By enclosing this smaller, high resistance part 
of a conductor in a glass globe or bulb and pump- 
ing out the air, the conductor would simply glow at a 
white heat without being melted. This led to the in- 
candescent electric lamp. At first one form of dynamo 
was used for the flaming arc lamps, and another form 
for the glowing incandescent lamps. Now, by the use of 
a peculiar form of induction coil placed on an arc light 
circuit, an alternating secondary current can be made 
to light the glow lamps. Perhaps more wonderful 
than all, the flame of the arc lamp is now used to melt 
hard and refractory ores, and its heat is used to weld 
riietals in a blacksmith's forge. 

The dynamo being an induction machine producing 
electricity it is not difficult to see that its current might 
be used to produce magnetism. This leads us to an- 



ELECTRIC MOTORS. 123 

other great art just coining into use and destined to 
produce as wonderful changes as the telegraph, the tel- 
ephone and electric light. When the current from a 
dynamo' is led to a second dynamo, magnetism is pro- 
duced, and the armature revolves under the influence 
of the magnetic attraction. By such an arrangement 
we are enabled to perform the greatest modern wonder of 
all — to transmit power to a distance. A steam-engine 
causes a dynamo to give out great streams of electric- 
ity, and these travelling over a wire move another dy- 
namo, and its power moves a printing-press, a sewing- 
machine, or a pump, or drags a loaded train along a 
railroad. 

At every step the variety of uses to which an electric 
current may be put spreads wider and wider. There 
are new paths stretching away in every direction. New 
arts seem to be constantly discovered. The current in 
the hands of a wise doctor helps to cure disease. In 
the silver-plater's hands it enables him to deposit films 
of metals for protecting spoons in a house* and type 
in a printing office. 

These first steps in electricity bring us to a most in- 
teresting point in the history of this great science. 
Many of the inventions that have made the laws of elec- 
tricity useful in the world have been brought out 
within the memory of people now living. The dynamo, 



124 FIRST STEPS IN ELECTRICITY. 

that has made the production of powerful currents of 
electricity both easy and cheap, is hardly twenty years 
old. The telephone is so new that the first patent on 
its construction has not yet expired. New electrical 
inventions appear every year and we may take up the 
newspaper some morning, just as we all did last sum- 
mer, and read an account of a new electrical invention 
or new use for electricity that may be as valuable as any 
that we have seen. Even now men of science all over 
the world are experimenting with this mysterious force 
in the hope of finding new ways in which it may be of 
benefit to men, women and little children. Active and 
curious minds are everywhere, and particularly in this 
country, asking questions, of nature that we may better 
know her laws and be enabled to use them in new and 
useful ways. 

Among the new electrical problems men are trying 
to solve two seem to promise great and important re- 
sults. When a battery is at work there is a chemical 
action going on between the acid and the two metals. 
The result of this action is an electrical current. It 
has been discovered that, if a current from a strong 
battery or from a dynamo is sent into a battery this 
chemical action may be reversed. The chemical 
changes produced in making the first current will, as 
it were, be turned round and made to go the other 



THE STORAGE BATTERY. 125 

way against its will. When this stronger current 
stops, the chemical action will reverse or go back 
again and give out an electric current. The most 
curious part of this action is that the new electric 
current will be stronger than the first current from the 
battery itself. It is very much as if a quantity of elec- 
tricity had been poured into the battery and bottled up 
for future use. Batteries arranged in a certain way 
may thus become storage places for electricity. Not 
really, but in a way that produces the same effect as if 
the current had actually been stored or kept in the 
battery. The current is sent into one of these storage 
batteries. A chemical change takes place under the 
influence of this current. Then, at any time after- 
ward (within certain limits), this chemical change 
can be used to send out a new current almost as strong 
as the current sent into the battery. 

The storage battery, with its chemical change ready to 
begin instantly at any time to send out a current, can then 
be carried anywhere to light a lamp or move an electric 
motor. A storage battery when charged may be put in 
a boat and its current in discharging may turn the 
boat's propeller and move it through the water, and at 
the same time light the red and green lamps at the 
bow of the boat. A storage battery may be put on a 
horse-car and move it through the streets and keep it 



126 FIRST STEPS IN ELECTRICITY. 

lighted at night, or may be put on a train of cars and 
light the sleepers all night while the train goes from 
Boston to New York. These storage batteries have 
been greatly improved within the past few years and 
are coming into daily use all about us both for light 
and for power. 

When the first telephones were used there was a 
great deal of trouble from induction. The telephone 
wires placed on poles beside the telegraph wires were 
subject to induction every time there was a make or 
break in the line wires near them. In the telephone 
wire there was a pulse of induced current at each dot 
and dash of the messages in the line wires, and this in- 
duced current produced curious sounds in the tele- 
phone that interfered with the words spoken in it. 
This induction is always more or less active in all tele- 
phones and manifests itself by the curious crackling 
and spattering sounds you sometimes hear when the 
receiver is at your ear. This induction, that when the 
telephone was new seemed to be so troublesome, is now 
used in telegraphy. By its use it is now possible to 
telegraph from a moving train of cars on a railroad to 
any and all stations along the road. The idea under- 
lying this singular invention is the use of a telephone 
to listen to the sounds made by induction from a wire 
beside the track. This road wire produces, by induction 



FLYING TELEGRAMS. 127 

through the air to the train, a curious buzzing sound in 
the telephone on the moving cars. Every stop and start 
in this continuous sound in the phone may spell the 
words of a message sent through the wire. This, in a 
very few words, is the underlying idea of this most use- 
ful invention. By its use accidents can be prevented 
on the railroad, because the conductor can be informed, 
even while flying along at fifty miles an hour, of the 
position of every train before or behind him, and the 
condition of every bridge and switch along the way. 

These marvelous inventions appeared only a few 
months since. Others as curious and useful may ap- 
pear to-morrow. We live in a time of scientific dis- 
covery and advance. Old experiments appear as daily 
conveniences. Familiar laws find new applications 
and old inventions are made more simple and of wider 
usefulness. Inventors, men of science, men of business 
who see the value of ideas, facts, and laws — all are busy 
experimenting, perfecting, and making useful these 
marvels of electricity. 

We read with wonder of the doings of the great men 
mentioned in history: Frederick the Great, Napoleon, 
great kings and generals. We should remember that 
to-day, in our own streets, are men who are doing 
more good than kings, emperors, or generals, because 
they are subduing nature and opening the kingdom of 



128 FIRST STEPS IN" ELECTRICITY. 

science to all. Some of these men who live among us 
may leave names that will be remembered long after 
kings and emperors have been forgotten. Being a 
king is a pretty selfish business at best. It has meant, 
in the past, war, trouble and misery for the people, and 
hatred for a memory. The worker in science, the in- 
ventor who makes the laws of nature useful, leaves no 
armies of widows behind him, no ruined cities for a 
monument. His w r ork lives after him because, by his 
labors, life is more easy, more comfortable and pleas- 
ant. All the people lead happier lives because he 
lived. 

This is the end of all steps in science. We have 
taken only a few. We might go on for years and find 
that all true and honest work in science leads to doing 
good. Best of all, this very work is now of great benefit 
to the inventor himself, for whoso discovers or invents a 
new thing of use to all men, will, unless he be blind or 
foolish, reap a great reward, both in wealth and in the 
respect and admiration of his fellow men. Every step 
in science, every effort we make to learn, however small 
and slow the pace, is attended by a sure reward. It 
depends upon ourselves what and how great the reward 
shall be. We may not find the reward in dollars, yet 
we shall find something if we be only earnest, patient, 
and ready to learn. Moreover, let us not think all is 



ONE LAW IN ALL LAWS. 129 

known, let us not imagine, in the midst of the wonders 
of science and invention we see to-day, that there will 
be no more discoveries, no new experiments and inven- 
tions. Every one of us, if we be earnest to learn, 
may be a discoverer of new truths and new facts. At 
any rate, we can all of us find by experiments facts 
that will have all the freshness and novelty of dis- 
coveries, because learned for ourselves directly from 
the great school-book we call nature. 

So this strange agent, this thing we call electricity, 
has come into all our lives, another gift from the Cre- 
ator. We rub silk on glass and electricity manifests 
itself. There is motion and electricity. We know 
there is also heat, because the glass feels warm to the 
hand. We see coal put under the steam-boiler, and 
there is heat from the fire. This heat gives steam 
from the water, and in the steam-engine this gives us 
motion. This motion moves the armature of a dynamo, 
and, we have electricity. The current of electricity in 
the electric lamp gives heat again, and from heat 
we have light. We burn a certain quantity of gas 
in a lamp and get heat and light. We burn the same 
amount of gas in a gas stove and get more heat and 
much less light. We burn the same amount of gas in 
a gas engine, and we get heat and motion without light. 
We use this motion from the gas engine to move a dy- 



130 FIRST STEPS IN ELECTRICITY. 

namo and produce electricity, and in electric lamps we 
get light and heat. Now do all things work together 
for good. We wonder if there is any difference between 
light and heat and motion. Men who have studied 
these things tell us they are the same, that heat is a 
mode of motion, that light is excessive heat which is 
only excessive motion. Motion becomes, through elec- 
tricity, light ; heat becomes motion ; and light is mo- 
tion. Thus, one thought joins all the circle of the 
sciences together. That which appeals to the eye is 
only another form of that we feel in heat. Motion ap- 
peals to the ear as sound, to the eye as light, till we 
wonder if there be anything save motion. These are 
the suggestions of the relations of the sciences brought 
to us by this agent called electricity, which seems to be 
a part of all and controlled by all. It certainly springs 
from heat and motion, and it will manifest itself as 
heat and light which are phases of motion. We begin 
to apprehend that the Creator's thought is as one 
thought, that there is a unity in nature far beyond any- 
thing our fathers imagined. 

Moreover, this unity of motion — electricity, magnet- 
ism, heat, light, and sound, we see in our telegraphs, 
telephones, and electric lights — extends far beyond our 
little world. The sun is over ninety millions of miles 
away, and yet we know that electrical disturbances in 



THE UNIVERSE OF LAW. 131 

the sun may affect every telegraph on our globe. The 
laws that the Creator implanted in things here are the 
same in the sun and in the entire solar system. We 
can go farther still and yet fail to get beyond the reach 
of law. The laws demonstrated by your little experi- 
ments in these our first steps hold good along the paths 
of suns whose light is as star- dust on the midnight 
sky. 



132 



FIRST STEPS IN ELECTRICITY. 



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